Cave

A cavern is, basically, just another word for a cave.

Description
Caverns are commonly-found cavities in the Stone layer of a map. Many caverns have tunnels branching off and winding in other directions, some of which connect to the surface of the map creating natural entries to the cavern. Caverns can be quite deep, extending from the surface all the way to the Bedrock layer, which is impossible to break through. In Infdev and Alpha mode, caverns are territorial, meaning that some areas of a map will have a number of caverns different to other areas.

How To Find One
There are a number of ways how you can find a cavern. Below is a table, designed to help cavern-hunting easier.

What To Expect
In caverns, you can expect to find at least one block of a type of ore. Pretty much all the ores can be found in a cavern, but it depends largely on how deep down you are - for example, to find Diamond or Redstone you need to be almost at the bottom of the map. Enemies can also spawn in caverns if it's dark enough, even if it's daytime outside.

Pros & Cons
Caverns can be useful for making dungeons and other underground structures with. Since it is a natural cave, it saves quite a bit of time on trying to find ore. However, caverns could be quite deep, like a pit, so if you accidentally break into one from above you could lose a lot of health or even die.