Group assignments take one submission object from each group, and this can be managed by either specifying which group member will make the submission on behalf of the group, or allowing anyone in the group to make a submission on the group's behalf.
Group assignments often involve two kinds of assessment - one for the group product, and one for the contributions of individual members - leading to a final, composite assessment for each individual. It's important to see not only the final product, but also some indication of how the group collaborated in order to produce it. Group assignments thus place greater weight on a versioning requirement, as document history informs the group participation assessment.
It is also common among group activities to involve some form of peer review: either having group members review one another's participation, or having the group product reviewed by other members of the class.
Group assignments thus represent the most complex use cases for submission-feedback workflow.