Paleontology is a combination of Geology (study of rocks) and Biology (Study of Life).
Paleontologists use fossils to try to figure out three main things about fossils: Identity and origin of the fossil, the fossil's environment, and what the fossil can tell us about the history of the earth
Because paleontologists are interested in finding out about all life on earth, they study all kinds of fossils, not just dinosaur bones.
There are many different types of paleontologists. Some study fossil plants, some study fossil fish, some study fossil mammals, and some study dinosaurs.
Paleontologists also use many other types of sciences to help them understand the past. For example, they used engineering to figure out how hard a Tyrannosaurus Rex bites.
Just a few of the tools used by a palaeontologist.