Image from Kevin Williams (copyright; used with permission)
Humanoid Armoured Fighting Vehicle, basically a manned walking weapons platform. Can range from an armoured exoskeleton only slightly larger than the occupant, to an excessively large construct the size of a skyscraper.
Robotic (unmanned) mecha are generally known simply as Mechs; turingrade humanoid fighting vecs are sometimes known as vecha, although they are generally classified in the larger class vechai or vechidae. Externally, mecha, mechs and vechai may look very similar.
Mechas are generally vulnerable because of their erect posture, as they present an easier target than a tank or scrub slug. But their uncanny gigantic humanoid appearance can itelf be a weapon, striking fear into many human (and some non-human) clades. Mechas are sometimes useful for construction and other tasks which low-lying vehicles are not suited for.
APC - Text by M. Alan Kazlev Armoured Personnel Carrier. Basically, any macroscopic wheeled, walker, or ground-effect military, police, or paramilitary AFV, used for transport of personnel. Although only lightly armored (contrast MIFV) an APC generally provides good protection against light arms fire, chemical, biological, and simple nano weapons, and may or may not be equipped with one or more non-lethal or lethal light projectile and/or energy weapons. Industrial Age to Recent.
RV-5 Transport Vehicle - Text by M. Alan Kazlev inspired by entry by Kevin Self Robust and popular Federation era all-environment wheeled vehicle used by extraterrestrial mining and exploration teams. The RV-5 carried four crew and a limited amount of cargo, and came with turingrade expert systems and pilots. Both electric and hydrogen fuel cell versions were available. Variants on the design remained common for centuries on many middle region, frontier and less developed worlds.