An Ecosystem is a set of at least two (autonomous) parties (the members of the ecosystem) whose individual work complements that of other members, and is of benefit to the set as a whole.
An ecosystem is distinct from a community in the sense that it is not a party in its own right (which a community is): it does not have and pursue objectives, nor does it manage a knowledge. A community is considered a specialization of the more generic 'ecosystem' concept.
The ability to distinguish between an ecosystem and a non-ecosystem enables one to focus on its members, e.g. to learn how they get to complement each other's work without this being explicitly organized, to organize ways in which such cooperation can be made sustainable without explicitly needing to organize or control that, etc. Being part of an ecosystem allows individual parties to focus on their strengths and to rely on others to provide for its needs, and being appreciated for the value of its own work as it provides for the needs of others, without the need of explicitly organizing all this.
An Ecosystem is a set of at least two (autonomous) parties whose individual work complements that of others, and is of benefit to the set as a whole.