I want to know about Cake Php. Why I will use it? What benefits I'll get from there?
Is Cake PHP the most Important part of PHP? No. Not even close. The most important part of PHP is PHP itself! Not some third-party framework.
In short, any framework offers common functions and other reusable code that isn't necessarily included in a language's library. It's intended to save you time by avoiding re-inventing the wheel when it comes to common features in a PHP application.