Political decisions, structures, processes and options cannot be adequately analyzed unless there is a basic understanding of the empirical context in which they are embedded. Whereas the management of plant genetic resources for food and agriculture (PGRFA) is a political issue, PGRFA as such is basically a biological topic that is closely interconnected with culture and socioeconomics. PGRFA encompass the diversity of genetic material in traditional varieties and modern cultivars, as well as crop wild relatives and other wild plant species used as food, fodder for domestic animals, fiber, clothing and shelter, according to the Food and Agriculture Organization of the United Nations. This chapter starts out with the ecosystems where they originated and the agro-ecosystems in which they are cultivated for the understanding of PGRFA. It explains the relevance of this knowledge for PGRFA management along the way. An ecosystem comprises the organisms living in a particular environment, and the physical part of the environment that impinges on them.