Collaboration simply means working together. So, if this is applicable to you, you can talk about any time you worked on a group project (for example, a group English paper, or a play for French class, or a science lab). If there was anything you struggled with, you can explain how someone else helped you understand. This will depend on your specific example, but if the collaboration was successful, you most likely achieved a deeper understanding of the subject, a good grade, or a new interest in the subject matter.
