The interface consists of:
In the GUI you build up instructions by selecting icons and items from lists. In the shell a natural language parser examines what is entered and attempts to resolve the request. Some units (especially military ones) are very particular on where the order comes from and the structure of the order and so care needs to be taken in the shell when commanding military commanders or their units. It's always best to ask the commander of a unit to carryout the instructions rather than ordering the unit directly, the commanders can get upset if they are left out of the loop (this can diminish loyalty to you).