This is the British spelling of paleontology: the science that studies fossils — the traces of animals and plants from long ago, left in rock — so we can learn about life in the deep past. A person who does this work is a palaeontologist (American: paleontologist). American English writes paleontology. Same science; the extra a is only the British palaeo- spelling. You meet the word in science class, museums, and news about a new fossil, not in everyday kitchen talk. Though actually, school talk often treats palaeontology as “dinosaurs”. Dinosaurs are a famous part of it, but the field also covers tiny sea shells, old plants, and animals with no bones. The tidy picture is narrower than the real job.

古生物學（英式拼法；美式作 paleontology）