Monsters

Zombie                                         ​ A zombie is the most basic monster in Minecraft. A zombie will attack you on sight.
Skeleton A skeleton is an archer. It will shoot you from a distance.
Spiders Spider A normal spider will only attack you at night unless you hit it during the day. They will attack you in caves during the day.  Spiders are 1 block high and 2 blocks wide so they will not fit through doors.
Cave Spider The cave spiders can only be found in abandoned mineshafts. They can poison you if your difficulty is on normal or hard. They can fit through doors.
Slime Slime can be found in 3 different sizes : big, small and tiny.  When you kill a big slime it will split into smaller slimes.  When you kill a small slime it will split into tiny slimes.  Their attack strength depends on their size, the bigger the slime, the stronger the attack.  Tiny slimes can only push you.  They can spawn during the day or night
Creeper A creeper can spawn during the day and night. It is the worst monster of them all.  It makes no noise when it walks and will blow up near you.  The attack strength depends on how close it is and the difficulty you are on. Dogs will not attack creepers. Creepers are afraid of cats!
Witches Witches spawn in witch huts.  They will throw potions at you that will slow you down and hurt you. They will heal themselves with potions.
Enderman The Enderman will not attack you unless you hit it or look at its head. It can teleport behind you and can move blocks. If you wear a pumpkin on your head and look at an Enderman it will not attack you unless you hit it. They can not teleport in or to water.