Your mobile phone is made of glass, plastic and metal. Glass comes from sand, plastic comes from oil, and metal comes from the ground.
Imagine you were walking in a desert (where there is lots of oil, sand and metals in the ground), and you found a mobile phone lying around. Would you believe that it came together by itself? That the Sun shone, the wind blew, lightning struck, the oil bubbled to the surface and mixed with the sand and metal, and over millions of years the mobile phone came together by chance?
No one would believe such an explanation. A mobile phone is clearly something that was put together in an organized way, so it would be rational to believe that it must have an organiser. In the same way when we look at the world around us, we see order everywhere from the water cycle to the movement of the earth around the sun. So doesn't it make sense that our world too has an organiser? This 'organiser 'is best explained by the existence of God.