What is design pattern?

A design pattern is a reusable solution to a commonly occurring problem in software design. Design patterns are general solutions that can be adapted to specific problems in a variety of contexts. They provide a common vocabulary and a set of best practices that help developers solve common software design problems effectively and efficiently.

Design patterns were first introduced in the book “Design Patterns: Elements of Reusable Object-Oriented Software” by the Gang of Four (Gamma, Helm, Johnson, and Vlissides) in 1994. The book describes 23 commonly used design patterns, organized into three categories: creational, structural, and behavioral patterns.

Creational patterns are concerned with object creation mechanisms, trying to create objects in a manner suitable to the situation. Structural patterns are concerned with object composition, trying to form large object structures from small individual objects. Behavioral patterns are concerned with object interactions, distributing responsibility between objects and helping to define the protocols they use to communicate with one another.

Design patterns can help make software more modular, easier to maintain, and more scalable. They are used in many different programming languages and software development contexts, and are considered an important tool in software engineering.