Index -> Appendix -> Traits
All cards (other than missions) list one or more traits in an area separate from their game text. Card type is one such trait. Every character has a trait of either team or support. Other traits include SGC, Goa'uld, Jaffa, and so on.
Effects in the game are often applied selectively only to cards that have a specific trait.
Imhotep's game text reads: "When you play Imhotep, choose one: Stop a Jaffa team character; or stop all Jaffa support characters." When you play him, you may stop a card that has the Jaffa, team, and character traits, or stop all cards that have the Jaffa, support, and character traits.