The purpose of Workspaces is to make it easier to manage several people working on different apps on Bitrise. Workspaces can own an unlimited number of apps, and Workspace owners can assign Workspace members to work on different apps as they see fit.
Workspaces consist of groups: Workspace owners can create groups and decide which members belong to which groups. A given group can be assigned to work on an app: all members of the same group will have the same level of access to the app.
Workspaces can take advantage of SAML Single Sign-On: we have guides for setting it up with several major identity providers.