Projects can be created with or without teamserver enabled. If you use teamserver, working together is easy. You can commit changes to the repository if you're at HEAD, other developers will get warnings when they commit to a stale checkout. The modeler helps you resolve any issues when you pull from the repository that create conflicts. Non-conflicting changes are merged automatically.
See this link for a little more info. I think there's some documentation somewhere but I couldn't find it.