The Predicate will always return a boolean, by definition.
Predicate is basically identical to Func.
Predicates are very useful in programming. They are often used to allow you to provide logic at runtime, that can be as simple or as complicated as necessary.
For example, WPF uses a Predicate as input for Filtering of a ListView's ICollectionView. This lets you write logic that can return a boolean determining whether a specific element should be included in the final view. The logic can be very simple (just return a boolean on the object) or very complex, all up to you.
