Fossils are preserved impressions of plants or animals embedded in a rock. They can take the shape of a body or a trace.
Determination of fossil's age:
Radioactive carbon dating: The age of fossils is estimated using the radioactive carbon dating technique, which uses the half-life of carbon and radioactive elements found in the fossils to compute their age.
Relative dating: Fossils are discovered in sedimentary rocks in the form of strata that have collected over time. As a result of this fact, geologists determine the age of fossils in such a way that those found at the bottom of those layers are older than those found above them.