The question of how the universe began is probably nearly as old as mankind. Answers to the question have ranged from the mystical to the religious to various scientific theories.
The early universe was extremely small, dense, and hot. For the first fraction of a second, only energy existed. It has since been expanded in all directions and has evolved from a primordial dense and hot state in a finite time in the past and continues to grow until today.
As the universe expanded and cooled, the four fundamental forces (gravity, electromagnetism, and the strong and weak nuclear forces) became distinct.