Topological descriptors are some of the most pervasive molecular descriptors, involved in many databases in chemistry. Furthermore, they have found to have great application in statistical modelling, clustering, diversity, de novo design and beyond. This chapter explores the different types of topological descriptor, from topological indices through to molecular fingerprints and how they have been used in chemistry applications. The principles by which the topological descriptors are generated will be explained in sufficient detail to understand the concepts and the situations in which they may be used effectively.