Up until now, we have only talked about concrete types. Despite being quite simple, they already allow for the expression of a lot of properties of a program on the type level and they have these properties verified at compile time. Scala gives the developer even more freedom by allowing them to use types as parameters while defining methods, classes, or other types. In the next section, we will look at different ways to do this, starting with basic type parameters and type member definition, and continuing with type constraints and variance topics. We'll conclude our discussion with higher kinded types and type lambdas.