Counterfeit: Not to be confused with Broder cards, a counterfeit is just that; a fake card with no authorization for existence. Subjects for counterfeits are usually high-dollar items, naturally, and they can be quite good. When the rookie card phenomena really took off in the late-70s, Pete Rose's rookie was the first well-known counterfeit, and thousands of them flooded the market. Since the hundred dollar baseball card was a pretty unusual thing back then, when it came to court, the judge didn't seem to take the matter very seriously. He ordered that the counterfeits could continue to be traded as long as they were clearly marked as such.
Since then, almost every major card has had some copycat. The 1952 Topps Mantle, 1985 Topps Mark McGwire, 1986 Donruss Jose Canseco, and 1990 Leaf Frank Thomas are just a few examples. Even a 1984 Fleer Update Ron Darling has been counterfeited.
Some counterfeits are easy to spot because they are just not well made. Some suffer from flaws like lines in the face of the card due to creases in the original. There are many ways to tell a counterfeit without being a hardcore expert in the field. One tell-tale sign of a counterfeit is the use of print dots. Because cards are printed with plates, there should be areas of solid color.
Photocopiers and scanners use lines of resolution, resulting in dense lines of dots instead of solid color. Under magnification of as little as 3x, the dots can be plainly seen, and a counterfeit uncovered. When in the market for high-end vintage cards (most cards made since 1989 that have any real value to them are extremely difficult to fake), borrow or invest in a strong glass or, better yet, a jeweler's loupe. These can help collectors spot flaws in addition to fakes.