What is fossil and what does it tell about evolution?

The preserved remains or traces of dead plants and animals that lived in the geological past and were buried under the rocks millions of years ago are called fossils. Fossils tells us about the process of evolution. Fossils gives an idea about the structure of organisms and corresponding period of their existence in the past. Fossils found under different strata of earth across different geological locations, provide evidence of evolutionary relationship among existing and extinct species of organism. They give us clues about extinct species of organisms and reasons behind their disappearance from earth due to different conditions of climatic change in the past.