The part of the tooth you can see above the gum is called the crown.
The crown of each tooth is covered with a hard protective layer called enamel.
Underneath the enamel is dentin, which is similar to bone, but not as tough as enamel.
Underneath the dentin is the soft, innermost part of the tooth, called the pulp.
Inside the pulp lies each tooth's nerve endings. These tell you when your teeth are hurting, for example, when you drink a hot drink or eat cold ice cream. The pulp also contains blood vessels which feed your teeth and keep them alive.
If you follow the dentin and the pulp of a tooth all the way down beneath your gum, you will find the tooth's root.
A cement-like substance, called cementum, glues the root of each tooth to your jawbone.