Usually -- unless the caller says otherwise -- the promenade will end when each couple has reached their home position (the position where they initially "squared up"). When they get there, they back out and form a squared set again.
The caller may also ask only some of the dancers to promenade, for example Heads Promenade. This means that the head couples promenade -- and the side couples don't. However, the fact that only the heads are being asked to Promenade doesn't mean that the side dancers don't have a part to play. If only some dancers are promenading around the outside, the other dancers are expected to temporarily move inward. This allows the dancers who are promenading to get around them without walking as far.
The caller can also ask the couples to only go partway around the square. For example, Heads Promenade 1/2 means that the head couples promenade, but they should go only halfway around, to the opposite side of the square, instead of going all the way around back to their home position.
Single File Promenade means that the dancers walk around the center of the square individually, rather than as couples. In most cases they will be walking until they get to their home position, in which case they back out and form a couple again.
If the caller asks only the boys or only the girls to Promenade, they walk in a smaller circle, inside the others. The others just stay where they are.
Star Promenade is similar to an ordinary couples promenade, but more compact. The dancers in each couple put an arm around each others waist, and the ones toward the center join their other hand to form a star.
Wrong Way Promenade is a promenade in the opposite of the usual direction. (The dancers will be walking clockwise around the center of the set, as viewed from above.)