Why use design patterns?

As it this is defined, Design patterns are solution to common software development issues in OOP. Elaborately design patterns are evolved from practices of resolving issues identified during or post development of OOP systems. So following a pattern will save you future embarrassment in development. ---------------------------------------------------------------------------------------------------------- "Head first design patterns" books has very interesting examples for further reading.

Design Patterns are the common software solutions for recurring problems which follow the proven best practices.

design patterns are used to make application modular/flexible for any changes/updates and easy integration/extension in future.