The game has 3 different types of maps:
1) Hostage rescue maps, where the counter-terrorist team's objective is to free four non-player characters that are present near the terrorist base.
2) Bomb defusal maps, where the terrorist team must try to plant explosives at specific sites in the map and protect it for a set amount of time while the counter-terrorists attempt to defuse it. Counter-terrorists can purchase a kit to cut the bomb defusal time in half.
3) Assassination maps, in which one member of the counter-terrorist team becomes a VIP, and must be protected from assassination until he reaches an escape zone. This game mode is also present in Counter-Strike: Source, although rarely played.
There are also other unofficial prefixes maps such as AWP, surfing, XC, AIM, KZ.
As for Professional tournaments, they only involve bomb defusal maps. And such maps are de_dust2, de_nuke, de_train and de_inferno.
You can find more maps on www.cstrike-planet.com