Final answer:
Fossils are the preserved remains of organisms that lived in the past, formed when dead organisms are buried and undergo processes such as decomposition and mineralization.
Step-by-step explanation:
After plants or animals die and are under a lot of pressure for a long time, they become fossils. Fossils are the preserved remains or traces of organisms that lived in the past. They are formed when dead organisms are buried by sediment and undergo various processes such as decomposition and mineralization.