Answer:
I run through hills. I veer around mountains. I leap over rivers. And crawl through the forests. Step out your door to find me.
What stays the same size no matter how much they weight?
Break it and it is better, immediately set and harder to break again.
I'm white, I'm round, but not always around. Sometimes you see me, sometimes you don't.
As I walked along the path I saw something with four fingers and one thumb, but it was not flesh, fish, bone or fowl.
This food is a tortilla filled with cheese and sometimes chicken before being heated or cooked.