A trading card is a small card, usually made out of paperboard

Paperboard

Paperboard is a thick paper based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker than paper. According to ISO standards, paperboard is a paper with a basis weight above 224 g/m2, but there are exceptions. Paperboard can be single...

 or thick paper

Paper

Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....

, which usually contains an image of a certain person, place or thing (fictional or real) and a short description of the picture, along with other text (attacks, statistics, or trivia). There is wide variation among different types of cards as to the configuration of objects, the content on the card, and even the material used to make the card.

Trading cards are traditionally associated with sport

Sport

A Sport is all forms of physical activity which, through casual or organised participation, aim to use, maintain or improve physical fitness and provide entertainment to participants. Sport may be competitive, where a winner or winners can be identified by objective means, and may require a degree...

s; baseball card

Baseball card

A baseball card is a type of trading card relating to baseball, usually printed on some type of paper stock or card stock. A card will usually feature one or more baseball players or other baseball-related sports figures...

s are especially well-known.
Cards dealing with other subjects are often considered a separate category from sports cards, known as non-sports trading cards.