A trading card is one of a set of thin pieces of cardboard with a picture relating to a particular theme, such as baseball or football, printed on it. Collectors buy the cards or trade them with other collectors.
[mainly US]
Now collectors can choose trading cards from a variety of sports.
trading card in British English
noun
any of a set of cards printed with images or information relating to a specific subject, intended to be traded between collectors seeking to acquire a full set
trading card in American English
any of various small, illustrated collectible cards issued in sets; often, specif., such a card displaying the statistics and photograph of a professional athlete