A mob (short for 'mobile' creature), or monster, is an entity that appears in Mine Blocks. There are three types of mobs: passive,aggressive/hostile and neutral. These mobs are used mainly for mob farms, mob drops, decorations, as a pet(only the wolf) etc.
Aggressive (or hostile) mobs are entities that pursue and harm the player. They spawn in poorly lit or non lighted areas such as night or in underground caverns or in mob spawners. These mobs do not spawn in peaceful. Such mobs are:
Also mobs like creepers, spiders, nethereyes and the Flaming Chicken do not burn when it is day unlike zombie, skeletons. Enderman do not burn when it is day, However, it doesn't like day, so it teleports away until it is night.The Flaming chicken can be made into a normal passive chicken by pouring water on it. If in creative mode you spawn Magma cube, slime, blaze, ghast in the overworld they do not get affected whether it is day or night.
Mobs that are are not aggressive but harm you when being attacked.
In the case of wolf, when you attack it, it doesn't follow you in terms of revenge. But if you stand with it you receive damage. When one Zombie pigman is attacked the others get warned and go in herds against you. The zombie pigman in herds are deadly so it's better if you don't make it angry.