Helium droplets provide an exotic and unique environment for the study of physical and chemical phenomena. Properties of these droplets include a low temperature (0.37 K), their superfluidity, and the ability to easily add a wide variety of atoms and molecules. This tutorial review provides a concise account of the basic principles of helium droplets, including how to form, dope, and interrogate these objects. There then follows a series of selected applications grouped under particular themes, with strong bias towards topics likely to be of particular interest to chemists.