Including cases where the player wears gauntlets, brass knuckles, or similar devices that (supposedly) make such attacks more devastating.
Without this tag, it is fairly simple to assume player is defenseless unless they attain some type of a weapon, which they may always have anyway.
Does NOT include jumping on people's heads (head jumping).
About Unarmed fighting (Hand-to-hand combat)[unarmed combat]
Is this also for games where unarmed fighting is standard? Beat'em Ups like Double Dragon or Fighting games like Street Fighter?.
Sort of. There's also the hack & slash sub-genre of beat 'em ups which does have weapons, and some beat 'em ups have firearms and/or melee weapons occasionally, so it does serve some minor purpose for them.