Palaeontology is the study of organisms that lived in prehistoric times.
Palaeontology broadly classified as palaeozoology (discussion on prehistoric animals) (sometimes the term palaeontology is used synonymously with palaeozoology)and palaeobotany (discussion on pre-historic plants).
But in case of ancient remains, their border is very fade because many specimens' taxonomic-nature could not be properly known (They grouped as incertae sedis). Another big branch of palaeontology, is micropalaeontology, study of microfossils (including small-sized organisms (like bacteria, cyanobacteria, fungal hyphae, foraminifera, coccoliths, diatoms ) as well as microscopic remains of large organisms , say piece of barks, wood, pollens (palaeoplynology), animal skeletal-parts of invertebrates and vertebrates), etc.
The term Palaeoecology is applied for discussion about encien environment, climate, different inter-relationships of organisms, etc.
Palaeontology is a very-much inter-disciplinary subject that is related with most-branches of biology, as well as Geology (Earth-science), Geography, Astronomy, Cosmology, as well as the discussion on origin of life is related to Synthetic-biology and Exobiology.
Palaeontology also have applied importance, like finding Coal and Petroleum, rock-layer correlation, etc.
Portion of palaeontology discussing about origin of human, merges with Archaeology. Bioarchaeology discusses with later-condition of life-forms (other than human), especially those associated with archaeological-sites.