Hexproof is a protective keyword. A permanent with hexproof can't be the target of spells or abilities your opponents control. Opponents can't point targeted removal, combat tricks, auras, or other targeted effects at it. Narrower versions exist: hexproof from black, hexproof from white, or hexproof from monocolored only stops spells and abilities of that quality controlled by opponents. Hexproof doesn't stop untargeted spells or abilities, and it doesn't stop you from targeting your own permanent.
In play, hexproof makes a permanent much harder to answer cleanly. Opponents must use untargeted removal, sweepers, sacrifice effects, or blocking instead. That can protect key threats, combo pieces, or auras and force opponents to spend different resources. Because it only blocks opponents, you can still equip, enchant, or pump your own hexproof permanent.
