An introduction to Scala Types (from the Scala Cookbook)

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is the introduction to Chapter 19, Types.

As you can tell from one look at the Scaladoc for the collections classes, Scala has a powerful type system. However, unless you’re the creator of a library, you can go a long way in Scala without having to go too far down into the depths of Scala types. But once you start creating collections-style APIs for other users, you will need to learn them.