A real-time strategy game (RTS) is a type of computer game which does not have "turns" like conventional turn-based video or board games. Rather, game time progresses at a pre-defined rate (often changable by the player(s)).
Because of the generally faster-paced nature (and the usually shallower learning curve), RTS games have exceeded the popularity of conventional turn based games. Many serious strategy gamers regard RTS games as "cheap imitations" of turn-based games because of the tendency of RTS games to devolve into "clickfests", in which the player who is faster with the mouse generally wins, because they can give orders to their units at a faster rate. Also, the faster pace masks the generally poor AI of the computer.
The more recent generations of RTS games usually have features which reduce the importance of fast mousework, enabling the player to focus more on overall strategy.
Usually RTS games follow the same general pattern:
Some of these games include Myth and Ground Control.
These games are purely tactical, forcing the player to make do with the units he or she is given. Most modern RTS games also feature single player campaigns - a series of missions where each mission has a different style of play, sometimes dramatically so.
Of the games that do allow the player to build up a base and an army, they seem to be diverging into at least two main camps: micro-management and macro-management.
Micro-management games allow an army and base to be built, but they limit the size of the army (sometimes, rather severely). The purpose of this is to create more of a tactical atmosphere, and to prevent one side from simply cranking out units and throwing them at the enemy until he collapses.
By limiting the size of the army, the game requires the player to intelligently utilize his "partially" limited troops. This is more similar to the purely tactical "myth" style games. A good example of this type of game is Warcraft III
On the other end are the macro-management games. These games encourage the creation of more massive armies, and often automatically take care of the "details" of individual unit control by organizing them into formations, intelligently maneuvering them, or using their special abilities automatically. Some examples of these types of games are Kohan and Kessen.