What does it mean to 3 bet light/4 bet light?

Are these just a limit HE terms?

Thanks

Raise with weaker holdings

No

Most people 3-bet - i.e. re-raise pre-flop after an original raise - only with the very best hands, say QQ+ and AK. Someone who's three-betting light is doing so with a greater range of hands, and is often incorporating position into the equation - it's very hard for the original raiser to call or 4-bet without a very small range of monster hands when they don't even have position and are almost certainly not getting the odds to call when they hold PPs or SCs.

4-betting light is pretty rare, because most people who three-bet are only doing so with monsters. So it's only really going to happen in maniac vs maniac confrontations, or hands at sufficiently high stakes where the players know that light re-raising is a much more common play and can react accordingly.