Mobs
- passive mobs
- hostile mobs
- neutral mobs
Passive mobs won't ever hurt you, and some examples are animals such as pigs, cows, and chickens, and NPC's (Non-Playable Characters).
It is a good idea to stay away from hostile mobs, because they will attack you no matter what. Examples of hostile mobs include monsters such as zombies, skeletons, creepers, etc.
Neutral mobs are mobs that are passive, but become hostile if you attack them. Neutral mobs are wolves, endermen, iron golems, and zombie pigmen.