What is the "gun show loophole"?
The Gun Control Act of 1968 requires anyone engaged in the business of selling guns to have a Federal Firearms License (FFL) and keep a record of their sales. However, this law does not cover all gun sellers. If a supplier is selling from his or her private collection and the principal objective is not to make a profit, the seller is not "engaged in the business" and is not required to have a license. Because they are unlicensed, these sellers are not required to keep records of sales and are not required to perform background checks on potential buyers, even those prohibited from purchasing guns by the Gun Control Act. The gun show loophole refers to the fact that prohibited purchasers can avoid required background checks by seeking out these unlicensed sellers at gun shows.
Which states have closed the gun show loophole?
Only six states (California, Colorado, Illinois, New York, Oregon and Rhode Island) require universal background checks on all firearm sales at gun shows, including sales by unlicensed dealers. Three more states (Connecticut, Maryland and Pennsylvania) require background checks on all handgun sales made at gun shows. Eight other states (Hawaii, Iowa, Massachusetts, Michigan, Missouri, New Jersey, Nebraska and North Carolina) require purchasers to obtain a permit and undergo a background check before buying a handgun. 33 states have taken no action whatsoever to close the gun show loophole.
In two states, voters themselves closed the loophole when their legislatures refused to do so. On November 7, 2000, the citizens of Colorado overwhelmingly voted 70% 30% in favor of Amendment 22, closing the gun show loophole in their state. The referendum followed the tragic shooting at Columbine High School on April 20, 1999 (the guns used in the shooting were purchased from private sellers at Denver gun shows). In Oregon, voters also voted overwhelmingly, 62% 38%, in favor of Measure 5, effectively closing the gun show loophole in their state.
http://www.csgv.org/issues-and-campaigns/gun-show-loophole/gun-show-loophole-faq
Some states have already closed it, individually. You may live in one of them. Biden is talking federally.