Mob

Mobs are the various types of creatures and monsters found in Minecraft. Currently, there are 14 unique mobs although alternative mobs can be implemented by mods. Mobs are affected by the same environmental hazards as the player, including burning and collision (falling) damage, with the exception of chickens, who do not suffer collision damage. Mobs can see you up to 16 blocks away, except for the Ghast which can see you 100 blocks away. Up to 200 hostile mobs and 15 neutral mobs can be on a map at a time. Mobs spawn no closer than 24 blocks from the player. Sometimes the player will find lots of passive mob at night around a few torches because they spawn in light. This is also a tactic to mine mob drops.

The term "mob" is short for "mobile" and has been used as a general term referring to any moving entities in games since the first MUDs surfaced.

About
As of Beta, there are a total of 14 types of mobs: Wolves, Pigs, Sheep, Cows, Chickens, Squid, Zombie Pigmen, Spiders, Zombies, Skeletons, Creepers, Slimes, Spider Jockeys and Ghasts. More information is listed below.

Current Mobs
Allied

Allied mobs follow players around and protect them after being tamed.



Wolf

Passive

Passive mobs will never attack the player.

Require a light level of 9 or higher to spawn with the exception of Squid.

Neutral

Neutral mobs will not attack the player unless provoked.

Aggressive

Aggressive mobs will attack the player when in range.

Require a light level of 7 or less to spawn with the exception of Ghasts and Slimes.

Unused and Removed Mobs
Unused

Unused mobs are mobs found in the source, but are not being used at this time.

Removed

Removed mobs are mobs that have been removed from the game.

Mentioned Mobs

 * Aside from zombie pigmen, living pigmen have been confirmed to appear in a future update.
 * In the Halloween update, Notch said he would add fish. However, he had limited time, and was thus only able to add them as an item. There is coding for fish in the game, but no model exists at this moment.
 * Dragons have been mentioned multiple times by Notch.
 * Notch confirmed during the Brocraft.net stream that he will be adding prefix mobs. This means that there will be mobs such as 'Burning Spider' 'Giant Zombie' 'Cobble Creeper', etc. It is not known if these are still planned to be in a future update.
 * A "scary monster" is going to appear in the 1.7 update.

Trivia

 * The Halloween update version 1.2.0 (Alpha) allowed hostile mobs to spawn in higher light levels at lower depths, using the formula 16 - (Layer ÷ 8). At level 8 and below, mobs could spawn even in sunlight. Notch reverted mob spawning to the original method in version 1.2.1 (Alpha) saying, "It was far too annoying. I have plans on what to do with this."
 * When mobs spawn, smoke comes out of them.
 * Both neutral and hostile mobs' noises can be heard up to 16 blocks away, which is the same distance that hostile mobs can sense you. Therefore, if you hear a hostile mob, you can already assume that they have spotted you.