Answer:
1) they can be Preserved
2) they can complete replacement by certain minerals
3) and their formation of an imprint or the filling in of an imprint
4) their formation of a thin film of carbon
5)They fill empty spaces by a mineral
Things that fossils can show about earths history is when the certain animal started to exist, and their time frame, it also tells when the earth may have first been 'born' because animals couldn't exist on earth before the earth did.
You know what I mean?