The Crews feature of the Client Portal is a module that helps to bundle workers together, by whatever category you classify them, for an easy to access group. This grouping can then be used to review site attendance, run reports on just those team members and help others that are not familiar with that crew, to see which team members are part of that crew.
An on-demand video showing the crew feature in action can be found here. Simply register for the webinar and be able to watch and interact with the presentation.