Under the My Profile section, I see an option for ‘Default Group’. What is that?

Default group allows you to target media asset uploads and file availability to an assigned group within CommandCenterHD. For example: if you are part of a group responsible for “This Week’s Specials”, all media you upload will become available for use for the “This Week’s Specials” group. This feature allows you to share images, video, and any other media assets uploaded to the system.