Fossils are the preserved remains or traces of ancient living things, such as plants and animals. They form when organisms are buried under layers of sediment, which hardens over time. This process can take thousands or even millions of years. Fossils help scientists learn about the history of life on Earth and how species have changed over time. There are different types of fossils, including imprints, amber, and molds. For example, a dinosaur bone found in the ground is a type of fossil that gives us clues about how these creatures lived. Studying fossils allows us to understand the evolution of life and the environment in which these organisms thrived.