Public health researchers are increasingly concerned with achieving ‘upstream’ change to achieve reductions in the global burden of disease and health inequalities. Consequently, understanding policy and how to change it has become a central goal of public health. Yet conceptualisation of what constitutes policy and where it can be found is very limited within this field. Our glossary demonstrates that policy is many headed. It is located in a vast array of documents, discussions dialogues and actions which can be captured variously by formal and informal forms of documentation and observation. Effectively understanding policy and its relevance for public health requires an awareness of the full range of places and contexts in which policy work happens and policy documents are produced.