How the earth began?why the earth was made?

First god created himself then he created the rest of the world

Many Polytheistic pagon religions believed that the world was created as a bi-product of a cosmic war between gods. The three major monotheistic religions believe that God created the world wilfully, to express his creativity, to glorify himself, and as a home for humans, who he created as an object of his love. Or you could believe that there was nothing there, and then it exploded, and then there was something there, which evolved into a load of crap for no reason or purpose. Up to you.