It started with simple bubble gum cards, the same kind used for baseball players. The front a photo from the movie, the back, a bit of the story or perhaps a behind the scenes peek. Now it includes the same in many versions, with special cards like art or holograms, and cards with points for playing games. It's a true challenge to get a complete set, especially if you try it by the pack. You may find yourself with 10 doubles of one card and none of another.
Widevision
By TOPPS and done for each movie in widescreen format.
These two are from The Phantom Menace (top) and Revenge of the Sith (bottom).
Regular
By TOPPS Regular Card size. In addition to the movies and the 2 animated versions of the Clone Wars TV series, they also did a special series of Shadows of the Empire cards.

Game
Star Wars Customizable Card Game. Big fans can play these in Tournaments, using sets from movies, sets with jedi, scoundrels, sith etc.
Metal
These were a few special sets that came out about the time of the 'special editions'. The came in a nice tin box and were tin themselves. There were at least: 1 of the jedi (Obi-Wan, Luke, Yoda) and one of Shadows of the Empire
Note the original Anakin Skywalker 'spirit' from Return of the Jedi, played by Sebastian Shaw and the extra card with the new 'special edition' scene from A New Hope.
Online
Online Cards for Star Wars the Clone Wars