Joseph R. Biden Jr. will become president of the United States at noon on Jan. 20 in a scaled-back inauguration ceremony. While key elements will remain traditional, many events will be downsized and “reimagined” to better adapt the celebration to a nation battling the coronavirus. Here’s a guide to the event.

What will the inauguration look like?

Although many of the events will be virtual, Maju Varghese, the executive director of the Presidential Inaugural Committee, said the goal was an “inclusive and accessible celebration that brings Americans together and unifies our nation, especially during such a tough time for our country.”

Mr. Biden will be sworn in by Chief Justice John G. Roberts Jr. on the Capitol’s West Front sometime before noon. The new president is then expected give his inaugural address and conduct a review of military troops, as is tradition.

But instead of a traditional parade before cheering spectators along Pennsylvania Avenue as the new president, vice president and their families make their way to the White House over a mile away, there will be an official escort with representatives from every branch of the military for one city block.

For remote viewers, the inaugural committee has planned what it is calling a virtual parade across the country featuring music, poets and dancers “paying homage to America’s heroes on the front lines of the pandemic.”

At 5:30 p.m. Jan. 19, the evening before Mr. Biden takes the oath, the committee will hold a lighting ceremony around the Lincoln Memorial Reflecting Pool in remembrance of people in the United States who have lost their lives in the coronavirus pandemic.

There will also be a prime time television event Jan. 20 featuring celebrities including Tom Hanks, Justin Timberlake and Jon Bon Jovi that aims to “showcase the American people’s resilience, heroism, and unified commitment to coming together as a nation to heal and rebuild.”

Is there expected to be unrest?

For weeks, Washington has been preparing for the possibility of protesters. But the nation’s capital was kicked into high alert after a violent mob breached the Capitol building on Wednesday and forced lawmakers to halt the official counting of Electoral College votes to affirm Mr. Biden’s victory.

Mayor Muriel E. Bowser has warned that extremists who support Mr. Trump might continue to wreak havoc and she extended the city’s public emergency through Jan. 21.

The F.B.I. and Secret Service have ramped up security efforts around the inauguration. Experts have warned that some far-right extremist groups are already discussing an assault on Inauguration Day similar to the deadly attack on the Capitol.

Unrest on Inauguration Day is not unprecedented: During Mr. Trump’s inauguration in 2017, crowds in Washington damaged storefronts, threw rocks and bricks at police officers and lit a limousine on fire in protest of Mr. Trump’s election. The day ended in more than 200 arrests.

Will President Trump attend?

President Trump announced Friday that he would not attend Mr. Biden’s inauguration.

Mr. Biden called that decision “one of the few things he and I have ever agreed on.”

Still, it is a major break with tradition for a president to skip the ceremonial heart of the country’s democracy: the peaceful transfer of power.

Vice President Mike Pence will attend, an aide said Saturday, after Mr. Biden made clear on Friday that he was welcome.

Only three presidents have missed their successor’s swearing-in: John Adams in 1801, his son John Quincy Adams in 1829 and Andrew Johnson, a Democrat who sat out the 1869 inauguration after he was replaced in favor of a Republican, Ulysses S. Grant.

Who will attend? And can I attend?

George W. Bush, has confirmed he would travel to Washington for Inauguration Day, along with Laura Bush, the former first lady. Barack Obama and Bill Clinton are also expected to attend, along with former first ladies Michelle Obama and Hillary Clinton. Jimmy Carter, who at 96 is the oldest living former president, announced that he and his wife would not attend. It will be the first presidential inauguration Mr. Carter has missed since he was sworn in.

Traditionally, the Joint Congressional Committee on Inaugural Ceremonies would distribute hundreds of thousands of tickets to the swearing-in ceremony for members of Congress to invite constituents, but this year tickets are not available to members of the public. Planners are urging people to stay home and participate in virtual inaugural events to prevent large crowds that could easily spread the coronavirus.

Events will be live streamed by the Presidential Inaugural Committee and by The New York Times.

Why is a presidential inauguration so important?

The 20th Amendment to the Constitution requires that the term of each elected president and vice president begin at noon Jan. 20 of the year after the election. Every president has taken the oath of office, and they cannot assume their positions without doing so.

Symbolically, it marks the peaceful transfer of power from the current president to the next. Inauguration Day will be all the more important this year, as Mr. Biden ascends to the presidency at a time when political division has threatened the nation’s democratic institutions and his predecessor has gone to extreme lengths to stay in power.

The inauguration is also a notable fund-raising opportunity for the incoming president. Though traditional events like balls have been canceled, Mr. Biden’s inaugural committee is offering special “V.I.P. participation” to corporations and well-heeled individuals who can use the opportunity to curry favor with the new administration.

Excess donations cannot be transferred to federal campaigns or party committees. Past inaugural committees have given unspent funds to charities for disaster relief as well as groups that decorate and maintain the White House and the vice president’s residence.