A mecha is a robotic machine, which can vary widely in size, configuration, and purpose; the term covers everything from man-sized Powered Armor to skyscraper-sized (or larger!) Humongous Mecha and all points in between. The only virtually universal aspect of mecha design is the inclusion of limbs. Mecha will have arms and/or legs where other types of machinery would have wheels, treads, wings, or other means of propulsion — mecha may have these things as well, but they'll have them in addition.