A Collection is a grouping of Spaces!
In the left-hand navigation, every Space will live in a Collection. You can customize each of your Collection names as well as change the order of them in the left hand navigation.
You can easily expand and collapse Collections to change your view and if you sign out and sign back in, the system will remember what Space you were in last as well as how you previously expanded or collapsed your Collection settings.
Right now, you can’t have a Space without a Collection—but that will be coming in a future update.
To create a new Collection, check out “How Do I Create a Collection?”
To learn how to manage your Collections, check out “How Do I Manage My Collections?”