Basically these are collector items in the vein of Pokemon Cards and Magic Cards, but predates all card based collectables. Like magic and pokemon cards, baseball cards contain statistics, but unlike magic and pokemon cards, the players with which these statistics refer to are real and not imaginary like players dipicted in magic and pokemon, which are made up to serve gaming purposes. Thus, baseball cards are not gaming cards and serve only to amuse and pleasure those who love baseball and their players (See keedon, baseball).
That damn keedon got so obsessed with getting that Ken Griffey Jr. baseball card that he flunked his midterms and got me to do his homework. Damn him and his obsession with baseball cards!!! (See keedon).
One who is obsessed with the game of baseball, baseball cards, baseball players, and anything remotely related to baseball is called a keedon (See baseball).
A keedon is one who pays exhorbitant amounts of money for boxed sets of baseball cards just to get a good autographed baseball card, which could have been bought individually at the same price or less (See keedon).