"Gun shows" have nothing to do with it.
Dealers are required to do background checks, "gun show" or not.
Private individuals are not required to do background checks, "gun show" or not (under federal law, state laws differ).
If you claim to be a private individual and the ATF determines that you are, de facto, effectively acting as unlicensed dealer, you go to prison for a very long time (assuming they don't just show up at your house and kill you, your dogs and quite possibly the rest of your family)
Anyone who talks about a supposed "gun show loophole" is either demonstrably ignorant of the actual laws in this area or being actively dishonest, and their opinions should not be trusted on this subject (or, arguably, anything else).