Mobs

Mobs are living entities that are affected by physics and can interact with players or other mobs.

Overview
Mobs can be divided into three behavioral categories: passive, neutral, and hostile. Some mobs will change their behavior in response to certain situations (eg. if they are attacked). Mobs usually drop items and experience points when killed, with hostile and "boss" mobs tending to drop rarer and higher-quality items, as well as significantly more experience depending on their difficulty.

Utility
Utility mobs are created by players. They can protect players and villagers from hostile mobs (with the exception of creepers). They usually attack hostile mobs, but in certain situations, they will attack any type of mob or player. An example is the Wither, which attacks all mobs except mobs that are considered undead.

Passive
Passive mobs are harmless to players and usually will flee if attacked. They provide beneficial items for players if the right tool is used (eg. shears to collect wool or a bucket to collect milk). Some mobs become passive only after they are tamed such as utility mobs. Some of these can also protect a player from hostile mobs.

Neutral Edit
Neutral mobs will attack a player only when provoked. They will not attack the player and have different behavior under usual circumstances otherwise. They may attack other mobs as well. For example, untamed wolves will attack any nearby rabbits, sheep, baby turtles, and skeletons.

Hostile
Hostile mobs will attack a player when they get within a certain range. For most hostile mobs, the range is typically 16 blocks, without any obstructions. Some mobs can sense a player from much farther away, such as ghasts, who detect all players within 100 blocks.

Boss
A boss mob is a special type of hostile mob that has an exceptionally large amount of health, a larger detection range, and triggers a health bar and name to appear at the top of a player's screen when they are within range. They are known as boss mobs due to their exceptional difficulty and are only recommended to be faced by experienced players. There are currently only two confirmed boss mobs within Minecraft.

Upcoming
These mobs are accessible in 1.16.2 excluding the Goat.

Unused
Unused mobs exist in the Minecraft source code, but cannot be spawned in default survival mode, without the use of commands.

Education Edition
These mobs only exist in the Education Edition version of Minecraft.

Unimplemented
Unimplemented mobs planned on the past updates, but currently do not exist within Minecraft.

Removed
Removed mobs no longer exist in modern Minecraft, but can be encountered in older versions of the game.

Trivia

 * Renaming a mob "Dinnerbone" or "Grumm" using a spawn egg or name tag causes it to flip upside down.
 * Renaming a sheep "jeb_" makes its wool change color with a smooth between colors. Shearing the sheep will still drop the sheep's true wool color.
 * Renaming a vindicator "Johnny" makes it attack all nearby mobs, except other illagers.
 * Renaming a rabbit "Toast" gives the rabbit a new texture, as an Easter egg to xyxzen420's girlfriend's missing rabbit.
 * Most mobs can be spawned using spawn eggs. However, Iron Golems, Snow Golems, and Withers are spawned by "building" them and stacking certain blocks in a specific order.
 * Bats are the only mob that does not interact with other mobs or players, and will not drop loot.
 * When lightning strikes certain mobs, they will turn into special variants. For example, a creeper will turn into a charged creeper; a villager will turn into a witch, and a skeleton horse will turn into four skeleton horseman with enchanted helmets and enchanted breastplate