The story of the Universe starts about 14 billion years ago with the Big Bang. This was a huge explosion that brought the Universe into existence. Before the Big Bang, there were no laws of physics, no time and no particles.
At the very beginning, there was an immense amount of energy in the form of radiation. It took hundreds of thousands of years after the Big Bang for matter to form. This matter makes up the world around us.
After many hundreds of millions of years, much of this matter was pulled together into clumps under its own gravity. These clumps became immensely hot in the process and the first Stars were born. The matter contained in your body has, at one time or another, been part of at least one star.