In 17 executive orders, memorandums, and proclamations signed hours after his inauguration, President Biden moved swiftly on Wednesday to dismantle Trump administration policies his aides said have caused the “greatest damage” to the nation.

Despite an inaugural address that called for unity and compromise, Mr. Biden’s first actions as president are sharply aimed at sweeping aside former President Donald J. Trump’s pandemic response, reversing his environmental agenda, tearing down his anti-immigration policies, bolstering the teetering economic recovery, and restoring federal efforts to promote diversity.

Here’s a look at what the measures aim to accomplish.

Mr. Biden has signed an executive order appointing Jeffrey D. Zients as the official Covid-19 response coordinator who will report to the president, in an effort to “aggressively” gear up the nation’s response to the pandemic. The order also restores the directorate for global health security and biodefense at the National Security Council, a group Mr. Trump had disbanded.

Though it is not a national mask mandate, which would most likely fall to a legal challenge, Mr. Biden is requiring social distancing and the wearing of masks on all federal property and by all federal employees. He is also starting a “100 days masking challenge” urging all Americans to wear masks and state and local officials to implement public measures to prevent the spread of the coronavirus.

Mr. Biden is also reinstating ties with the World Health Organization after the Trump administration chose to withdraw the nation’s membership and funding last year. Dr. Anthony S. Fauci will be the head of the U.S. delegation to the organization’s executive board and will jump into the role with a meeting this week.

With an executive order, Mr. Biden has bolstered the Deferred Action for Childhood Arrivals program that protects from deportation immigrants brought to the United States as children, often called Dreamers. Mr. Trump sought for years to end the program, known as DACA. The order also calls on Congress to enact legislation providing permanent status and a path to citizenship for those immigrants. 

In a blow to one of his predecessor’s earliest actions to limit immigration, Mr. Biden has also ended the so-called Muslim ban, which blocked travel to the United States from several predominantly Muslim and African countries. Mr. Biden has directed the State Department to restart visa processing for individuals from the affected countries and to develop ways to address the harm caused to those who were prevented from coming to the United States because of the ban.

Mr. Biden has also halted the construction of Mr. Trump’s border wall with Mexico. The order includes an “immediate termination” of the national emergency declaration that allowed the Trump administration to redirect billions of dollars to the wall. It says the administration will begin “a close review” of the legality of the effort to divert federal money to fund the wall.

Chief among executive orders that begin to tackle the issue of climate change, Mr. Biden has signed a letter to re-enter the United States in the Paris climate accords, which it will officially rejoin 30 days from now. In 2019, Mr. Trump formally notified the United Nations that the United States would withdraw from the coalition of nearly 200 countries working to move away from planet-warming fossil fuels like coal, oil, and natural gas.

Mr. Biden will end the Trump administration’s 1776 Commission, which released a report on Monday that historians said distorted the role of slavery in the United States, among another history. Mr. Biden also revoked Mr. Trump’s executive order limiting the ability of federal agencies, contractors, and other institutions to hold diversity and inclusion training.

The president designated Susan E. Rice, who is the head of his Domestic Policy Council, as the leader of a “robust, interagency” effort requiring all federal agencies to make “rooting out systemic racism” central to their work. His order directs the agencies to review and report on equity in their ranks within 200 days, including a plan on how to remove barriers to opportunities in policies and programs. The order also moves to ensure that Americans of all backgrounds have equal access to federal government resources, benefits, and services. It starts a data working group as well as the study of new methods to measure and assess federal equity and diversity efforts.

Another executive order reinforces Title VII of the Civil Rights Act of 1964 to require that the federal government does not discriminate on the basis of sexual orientation or gender identity, a policy that reverses action by Mr. Trump’s administration.

Mr. Biden is moving to extend a federal moratorium on evictions and has asked agencies, including the Agriculture, Veterans Affairs, and Housing and Urban Development Departments, to prolong a moratorium on foreclosures on federally guaranteed mortgages that was enacted in response to the coronavirus pandemic. The extensions all run through at least the end of March.

The president is also moving to continue a pause on federal student loan interest and principal payments through the end of September, although progressive groups and some congressional Democrats have pushed Mr. Biden to go much further and cancel up to $50,000 in student debt per person.

Following in the footsteps of some of his predecessors, Mr. Biden has established ethics rules for those who serve in his administration that aim “to restore and maintain trust in the government.” He has ordered all of his appointees in the executive branch to sign an ethics pledge.

Finally, Mr. Biden issued a freeze on all new regulations put in motion by his predecessor to give his administration time to evaluate which ones it wants to move forward with. The memorandum is aimed at preventing so-called midnight regulations, policies pushed through by a lame-duck president unconstrained by electoral considerations. The fast pace often cuts short the opportunity for the public or industry to review the policies.

After four years of Donald Trump's presidency, he's outta here -- and President Joe Biden has arrived.

His inauguration went down today in the U.S. Capitol, where Biden stepped into his role as the 46th President of the United States. Joining him, while making history of her own, was Vice President Kamala Harris -- the first woman, first Black woman, and first Asian American woman to hold the position.

The Twitter trends started rolling in as soon as the arrivals did -- as Harris, Michelle Obama, and Hillary Clinton all got people talking over what they wore to the event.

Harris donned a purple look from Christopher John Rogers -- with purple being considered a sign of bipartisanship between Democrats (blue) and Republicans (red). Obama stunned in a more raspberry look, wearing a coat and belt from Sergio Hudson -- while Hillary also wore purple, just as she did during her 2016 concession speech.

Another fashion moment that went viral: the husband of Kamala Harris' niece Meena Harris, Nikolas Ajagu, wearing a pair of Dior x Air Jordan 1s to the inauguration.

Following a few opening remarks, Lady Gaga took to the podium to sing the National Anthem -- delivering it with just as much power as one would expect from the consummate performer. She wore a custom Schiaparelli couture look, with a giant dove pin attached to her chest and her hair done up in a braid. "A dove carrying an olive branch. May we all make peace with each other," she said of her look on Twitter.

"Singing our National Anthem for the  American People is my honor," she also tweeted before the performance. "I will sing during a ceremony, a transition, a moment of change—between POTUS 45 and 46. For me, this has great meaning."

"My intention is to acknowledge our past, be healing for our present, and passionate for a future where we work together lovingly," she added. "I will sing to the hearts of all people who live on this land. Respectfully and kindly, Lady Gaga."

Harris was then sworn in as Vice President by Justice Sonia Sotomayor, an emotional and historic moment for all of those watching at home.

Jennifer Lopez was up next, as she hit the stage to sing "America the Beautiful" and "This Land Is My Land" in an all-white Chanel pantsuit and matching coat.

After reciting two lines of the Pledge of Allegiance in Spanish and exclaiming "Justice for All" in Spanish, she snuck a "Let's Get Loud" reference into the end of her performance.

With Dr. Jill Biden by his side, Joe Biden then took his oath of office, administered by Justice Roberts. After that, Amy Klobuchar officially introduced Biden as 46th President of the United States for the first time, to a standing ovation.

He gave a speech saying "the will of the people has been heard," adding, "we've learned again democracy is precious, democracy is fragile and democracy has prevailed."

"As we look ahead, restless, bold, optimistic, and set our sights on a nation we know we can be and we must be, I thank my predecessors of both parties for their presence here today," he continued. "I know the resilience of our constitution and the strength of our nation."

"The American story depends not on any one of us, not on some of us, but on all of us," he added. "We the people who seek a more perfect union. This is a great nation, we're good people and over the centuries with storm and strife, peace and war, we've come so far, but we still have far to go."

Saying there was much to repair, restore, heal and gain, Biden said there's never been a "more challenging or difficult" time than the one we're in now, thanks to Covid, racial injustice and a surge in domestic terrorism and white supremacy. He was hopeful, however, for change and unity and once again pledged to be president for "all Americans" -- even those who did not support him.

Garth Brooks followed Biden's speech, giving an a cappella performance of "Amazing Grace" and asking those watching the inauguration in person and at home to sing along.

Among the last to speak at the event were 22-year-old Amanda Gorman, the National Youth Poet Laureate and youngest person in history to read a poem at an inauguration. Her powerful and emotional speech was followed by a reading from Rev. Silvester Beaman of Bethel AME Church in Wilmington, Delaware -- a longtime friend of the Biden family.