WASHINGTON — The House this week is set to pass the first major gun control legislation in over two decades, with Democratic lawmakers expected to approve two measures strengthening background checks for all firearms sales.

The last time the House put high-profile legislation expanding gun control laws to a vote was in 1994, when it passed the Federal Assault Weapons Ban and made it illegal to manufacture a number of semiautomatic weapons for civilian use. That legislation expired after a decade and was not renewed by a Republican-controlled Congress.

But riding a new wave of urgency after a series of mass shootings — and the activism inspired by the school massacre in Parkland, Fla., last February in which 17 students and teachers were killed — House Democrats have pledged to take meaningful action on the issue, beginning with the twin bills.

Here’s what you need to know about the measures and their odds in the Senate.

What do the bills do?

The Bipartisan Background Checks Act, which the House will take up on Wednesday, requires universal background checks, closing a loophole for buyers at gun shows and online. The legislation, sponsored by Representative Mike Thompson, Democrat of California and the chairman of the House Gun Violence Prevention Task Force, also prohibits firearms transfers by a person who is not a licensed dealer. There are a number of exceptions, though, such as a family member giving a firearm as a gift, or lending a gun to someone in imminent danger.