Abstract: Heegaard Floer homology is a package of invariants defined for closed, oriented 3-manifolds. The simplest version arises as the homology of a certain chain complex associated to a Heegaard splitting. We will outline the construction of the various different flavours of Heegaard Floer homology and explore some of their key properties. Time permitting, we will also introduce the related theory of knot Floer homology, a powerful knot invariant which categorifies the Alexander polynomial and is able to detect features such as whether a knot is fibred.