Collaboration:
A great way of looking at collaboration is to see it essentially as communication between people with the intent of achieving some result or goal. There are several ways in whcih these kinds of interactions can be classified:
The interaction may have to do with implementing a project with a team that has a high degree of structure - a bureaucracy with a strict chain of command. Very rigid rules for interactions, very specific delegation of authority and very specific allocation of responsibility. The communication here will be very structured and very fixed.
Alternately, the interaction may be for the same purpose of implementing a project but with a very loosely defined structure. In this case, the communication will be very ad hoc and unstructured.
A different classification, othogonal to the earlier one, could be based on the number of people collaborating - a group, a pair, a whole company, or everyone.
Based on these classifications, different systems are required to facilitate collaboration. In some cases email is appropriate, in other cases, enterprise systems are required.