The basic idea of play is to be in move mode, let the program select the next unit to do something, then give it a command, either by clicking the mouse or by typing on the keyboard.
Each map may be in either survey or move mode (See section Modes) independently of the others. In survey mode, the default actions are not to do anything, while in move mode, the default actions are to do things. This principle applies to both mouse and keyboard commands. For instance, 'h' in survey mode moves the current position west by one cell, but in move mode it causes the current unit to try to move west by one cell.