This is a small tutorial I want to make to help people who are new to Minecraft understand mods.
I am making this myself and it is not copied off of anything.

When you first get Minecraft it may be a strange experience and you may wonder what these animal
and monsters spawning really are and what you can do with them.

First of all animals spawn all the time and are attracted to light! Mobs spawn during the night
They want to attack you. They will spawn on any difficulty EXCEPT peaceful.

Creepers!

First this is a creeper:

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These are green with white and grey spots all over them.
They spawn during the night but can live throughout the day and will try to attack you all the time.
When you get within 5 blocks of them they will explode and blow up everything around them.
*PRO TIP* They are easiest till kill with the bow and arrow as you don't have to get close enough for them to blow up!
Also when you kill a creeper you will notice that they drop a grey substance which is gunpowder!
Gunpowder can be used to make TNT which is very useful for a fast method of mining.
You can tell when a creeper is about to explode as it will hiss and flash at the same time.
They are the only mod which drops music disks and you do get them to drop them by having a skeleton
finish it off!
They are hated thoroughly by most players due to their capability to blow up houses, landscapes, pets and the players hardwork!
Danger: 9/10

Skeletons!

First of all this is a skeleton:

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Skeletons are white with black features and look very skinny.
They only spawn during the night or in dark places and when they are in the light they light on fire
and die about 20 seconds later but they can still attack you when they are on fire!
Skeletons fire arrows at you with a bow so they have a long range compared to the other mobs and they
also move fast!
*PRO TIP* They are easiest to kill by getting them stuck on the side of a corner
most commonly a tree and hitting them from a 90 degree angle.
When you kill a skeleton they drop between 0-2 arrows and/or 0-2 bones.
Arrows can be fired from your bow and bones can be used to tame wolves and to create bone meal.
Bone meal can be used for growing trees spontaneously and if right clicked on grass it grows long grass and flowers.
You can usually tell if a skeleton is nearby by a clinking of bones noise.
Skeletons are quite accurate and they move to the left so they are harder to hit so try and get behind
some cover such as a tree or a hill!
Skeletons are obviously dislike but not as much as creepers!
Danger: 8/10

Zombies!

This is a zombie:

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Zombies are green with a cyan ripped shirt and blue ripped trousers.
They spawn in the night or in dark places as all mobs do and they burn in the light. The same as skeletons.
Zombies have the worst range and are very slow. They use their hands to attack which can do a lot of damage.
*PRO TIP* Attack them with swords as they are easy to kill and your arrows can be saved for killing creepers!
When you kill a zombie they drop 0-2 feathers which can be used for making arrows!
You can tell a zombie is near as you will hear a deep moaning sound nearby.
Zombies usually spawn together and have no defensive techniques.
They are probably the easiest mob to kill.
Danger: 5/10


Spiders!

This is a picture of a spider:

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Spiders are dark grey with black spots and red eyes.
They spawn in dark places or at night time but unlike any other mod are neutral in the daytime and will not attack unless in a shaded area.
Spiders will attack from three blocks away by lunging at the player. They only cause a small amount of damage to the player though.
*PRO TIP* They are easiest to kill with a bow and arrow as they are two blocks wide.
Spiders drop 0-2 pieces of string when killed.
String can be used to make bows and fishing rods.
You can tell when a spider is near by as it makes a long hissing noise which sounds like gargling.
Spiders can sometimes spawn with a skeleton on their backs but it is very rare but when they do they are probably the hardest mob in the game. They are called Spider Jockeys.
Danger: 7/10
Spider Jockey: Danger: 9.5/10

This is all my own work and took my a very long time to type up.
It is all from my experience of playing the game and there may be one or two small mistakes I made.

Thanks for reading, I hope I helped!