Philosophy is literally the love of wisdom.
Ontology is the field of metaphysics about what exists.
Ethics - philosophical reasoning about principles of right conduct, the nature of justice, virtue, and so on. Aesthetics - philosophy of art and beauty. Logic - the field of philosophy concerned with principles of correct reasoning. Philosophy of science asks questions about what it means to do science, the justification for scientific method, and so on. Philosophy of law applies philosophical reasoning techniques to a study of legal systems.