Why is my laptop not working? How can I get it fixed?

I have no idea what happened to my laptop.I was at school and I sat it down in the grass for a while.When I got home I turned it on and my whole screen was white big black marks so I couldn't see the screen.Also every time I try and touch the screen the black stuff spreads.Can someone please tell me whats wrong with it ,and how can I get it fixed?