Developers face some problems while developing applications or in the software application Lifecycle which are common and repeated, for example, creation and disposal of objects, interaction between objects, the structure of classes that enhance cohesion and loose coupling, fixing of bugs in a way that minimize changing of source codes, etc.
Design Patterns in the object-oriented world are a reusable solution to common software design problems that repeatedly occur in real-world application development. It is a template or description of how to solve problems that can be used in many situations.