Sheep

Short Info
Sheep are one of the first created passive mobs (along with pigs and cows) and are very vital to surviving in Minecraft.

Use
The sheep is the safest and most efficient way of obtaining wool for beds, which are needed to skip from dusk to dawn and to set your spawnpoint without using commands.

Interactions
You can shear a sheep with shears or kill it to get wool, for crafting beds and carpets. Every once in a while, you can see sheep eat grass, which will make them automatically grow their wool back if you had sheared them instead of brutually murdering it. And by gathering things to make dye with, you can change the color of your sheep from blue to pink.:)