Chess pieces on the board

You're playing with several hundred semi-intelligent characters, or units. You don't control or steer them directly, but give them orders which they try to carry out as best they can. They walk, drive, sail or fly across the map under their own power, negotiating obstacles along the way and challenging any enemies they encounter. Actually, they're just bits of data cycling around your computer's memory and presented in an elaborate graph that looks amazingly like an anthropomorphic, cartoon war. As in Chess, you have a board and a collection of playing pieces, from lowly pawns to powerful queens, although in RTS pawns might be foot soldiers and the queen an aircraft carrier, and you might command a fleet of them.

In Chess, a piece's movement and position decides its strategic importance. Any piece may take other; they're all effectively the same. The only differentiation between pieces is how they move on the board. In an RTS, units have an entire suite of attributes. Their identity is important. They're more like a cut down RPG character, a little bundle of stats with a few rules that determine how they behave and move, or whether or not they're weaker or stronger than their fellows. When large numbers of them clash the game is furiously looking up charts and doing the sums to produce a result as human players did in days of old. But for all that a unit is still just a playing counter at heart. These aren't lovingly lived in personalities of an RPG; RTS units are expendable drones stamped out en mass by factories and nothing more than cannon fodder for your demented schemes of conquest.