A Design Pattern essentially consists of a problem in a software design and a solution to the same. In Design Patterns each pattern is described with its name, the motivation behind the pattern and its applicability.
According to MSDN, "A design pattern is a description of a set of interacting classes that provide a framework for a solution to a generalized problem in a specific context or environment. In other words, a pattern suggests a solution to a particular problem or issue in object-oriented software development.