Information on plants located at .edu sites often reference an extension at a university in the U.S. What exactly is an extension and what is its function? From context I assume it's a research facility of a government agency related to agriculture. Are there similar facilities in Canada? If so, what are they called?
My understanding is that it is a goverment-funded service (directly or indirectly) that provides information to the public, generally with an agricultural bent (for example, there are veterinary medical extension offices). These forums are an extension service in that the administrative role is performed through indirect government funds, although it is certainly not a traditional model as there are many user-to-user interactions as opposed to service-provider-to-user. Garden help telephone services available through most Canadian gardens would be considered extension services, as well.