What it does
Hexproof from a specific quality means the permanent can't be the target of spells or abilities of that type controlled by your opponents. For example, "hexproof from black" means opponents can't target it with their black spells or abilities, while "hexproof from creatures" protects it from being targeted by abilities of opponents' creatures.
The most common mistake is thinking it's full protection. Unlike protection, hexproof from only stops targeting—it doesn't prevent damage, prevent enchanting/equipping, or cause the card to be destroyed or sacrificed by non-targeting effects. It also only applies to opponents; you can still target your own creature freely. Board wipes, edicts ("each player sacrifices"), and non-targeting removal still work.
In Commander, it's useful against specific color-heavy metas—hexproof from a color sidesteps that color's targeted removal while leaving you flexible to buff or save your own creature.
