ManagerThey have access to all spaces and information. They can also invite other users to be managers.
CoreThey are members/owners of your spaces. They can see some reports about their space tickets, activities, and users in the portfolio + defined access to each space you invited them in the portfolio.
WatcherThey will see a start page listing the spaces and activities that they are working on with you, plus the defined access to each of the spaces you invite them in the portfolio.