Design Pattern

Question

Hi to everyone!
Recently I have studied the design pattern and his functions. But I don't really understand why these construct are very important and useful inside a "big" projects.
Can someone tell me one or more reason because i need design pattern in programming?
Furthermore, this construct exists only in object oriented programming?
Where i can find a little explanation for every design pattern in order to remember his general purpose?

Answer 1

https://www.sololearn.com/learn/672/?ref=app

Answer 2

https://code.sololearn.com/c8OeV7di4VTn/?ref=app