Background checks are already required when you buy a gun from a dealer. Almost all Democrats, and some Republicans, also want a background check when you sell a gun privately. This includes whether at a gun show or the parking lot at Wal-Mart. The "gun show loophole" just makes a better soundbite.
Thank you both for your answers. It was the private sale issue that I wasn’t considering. Now it makes sense to be opposed to that.