This chapter uses an overview of the historical evolution of development agencies and a short profile of each of the 16 development agencies (DAs) which form the core evidence base of this book to introduce how these development organisations compare and why they vary. One consequence of the mix of different factors in the establishment of development agencies is some very basic differences in the purpose, role, structure, scale, shape, size, and resourcing of the agencies. At the same time, while many development agencies are “comprehensive”, engaging directly with a wide range of interventions in labour markets, property markets, external investment markets, and with enterprise and innovation drivers, many are more focused, concentrating more on one or two of these activities. Having identified and explained this diversity, the chapter distinguishes five predominant development agency types: development and revitalisation agencies; productivity and economic growth agencies; integrated economic agencies; internationalisation agencies; and visioning and partnership agencies. It concludes that this diversity is evidence of the flexibility of DAs and the different needs of local development systems. The fact that the mandate of each can be tailoured to contribute optimum value to the local development agenda makes them a powerful potential tool for local leaders.