The game types are unique and are created by the map designer. Certain elements are included in a map to delineate which type it is. Some times the T's will not start out with any weapons on this type of map. They can usually locate a weapon stash, but that is not guaranteed. Teams also switch at regular intervals so both sides get to see what it is like to be on the other side in these battles.
Assassination is another unique variation.
One player is made the VIP, and they cannot buy any items, but they are still rewarded money for accomplishments and are heavily armored. The money can be used by that person later in the series. The terrorists goal is to kill the VIP before they can get to the VIP escape zone. All CT players are supposed to guard the VIP with their life, if necessary. This allows every member of the CT's to get a chance to be venerable, and to use their money from previous rounds.