Unit

From AgeofWiki

A Unit is most commonly thought of as the "things in a game which can move on their own". Some things are obviously units, like villagers or frigates. Other things are obviously not units, such as your Town Center. As a general rule, anything in the "Units" subsection of the "Objects" menu is a unit. A further rule is that anything in the game you can either fight with or gather resources with is a unit.