Sub-field of ecology that studies populations of different species living in a common environment, hence potentially interacting and subjected to similar abiotic elements.
Community = interacting populations of 2+ different species...
- Occupying the same space/time.
- via Various types of interspecific interactions (e.g., competition, predation/parasitism, commensalism, mutualism, and amensalism)
A community doesn't have to contain all organisms within a certain habitat.
Sometimes we might limit our discussion of a community to a single guild or single trophic level. Other times we might use the terminology simply to describe two interacting species (either within or between guilds/trophic levels).
Really, "communities" are more conceptual "units" used to describe two or more interacting species. More accurately, it's an interaction between populations of 2+ species. In this way, community ecology is an extension of population ecology.