The subject area of philosophy is often divided into three: ontology, epistemology and axiology:
Ontology is about the nature of reality. It tries to answer the question, "What is?" or "What is reality made of?"
Epistemology is about the nature of knowledge, and the means to arrive at it. It tries to answer questions like, "What is knowledge?" and "How do we know?"
Axiology is about values. It deals with questions like "Where is the world heading?" and "What should our values be?"
Aesthetics, "What is beautiful?" and Ethics, "What constitutes right action?" are often considered two sub-fields of axiology.