The original Gang of Four book separated patterns into three categories: creational, structural, and behavioral. To these three, another large category was added in recent years, concurrency patterns. Some concurrency patterns were covered in another classic book: Pattern-Oriented Software Architecture: Patterns for Concurrent and Networked Objects, Volume 2, by Douglas C Schmidt, Michael Stal, Hans Rohnert, and Frank Buschmann.
Creational patterns deal with delegation. They are focused on creating new objects and groups of related objects. These patterns will create objects for you, meaning that you don't have to create them directly.
The focus of structural patterns is aggregation. They define ways to compose objects in a way that creates new functionality from the constituent parts. They help us create software components.
Behavioral...
