What is main work of Facade Pattern?

What is main work of Facade Pattern Explain me

The facade pattern is a software design pattern commonly used with object-oriented programming. A facade is used when one wants an easier or simpler interface to work with.
A facade can:

1. Make a software library easier to use, understand and test, since the facade has convenient methods for common tasks;
2. Make the library more readable, for the same reason; 
3. Reduce dependencies of outside code on the inner workings of a library, since most code uses the facade, thus allowing more flexibility in developing the system; 
4. Wrap a poorly-designed collection of APIs with a single well-designed API.