Design patterns are reusable solutions to common problems in software design. They provide a template for how to solve a particular issue, making it easier for developers to create efficient and maintainable code. By using design patterns, programmers can avoid reinventing the wheel and instead focus on implementing the unique aspects of their projects. There are several types of design patterns, including creational, structural, and behavioral patterns. Each category addresses different aspects of software design. For example, creational patterns deal with object creation mechanisms, while structural patterns focus on how objects and classes are composed to form larger structures.