I saw my friend in her casket today and...?

My friend died of cancer, and today was her funeral. I decided to make the ballsy choice of going up to her casket and seeing her. (which was a bad idea) but anyway, I was just shocked, because I've never seen a dead body before. She looked very peaceful, but I was wondering what I was looking at. I mean, I know it was her body, but her spirit and life is missing. I am wondering what they put inside her, to preserve her or whatever and what happens after a long time of being in her grave, (she was burried today also). what is the process? thank you.