What is a relic baseball cards?

Answer 1

This is a card containing either part of the players jersey, bat, pants, or some other small piece of memorabilia. There is also something called a manufactured patch or relic. This wasn't game used, but still is cool.

jersey bat

manufactured patch.

Answer 2

A relic card is a card with some sort of game used fabric or wood. For example a Derek Jeter Relic card might have a part of his game used jersey or bat in it.