GRASP (General Responsibility Assignment Software Patterns) is a set of principles for assigning responsibilities to classes and objects in software design. It describes nine patterns including creator, informational expert, controller, low coupling, high cohesion, and polymorphism. The patterns provide guidelines for assigning responsibilities to classes to achieve benefits like high cohesion, low coupling, and flexibility to changes. For example, the informational expert pattern suggests assigning a responsibility to the class that has the necessary information to fulfill it.