Box 1: Basic
Assign Basic to users with a TFS CAL, with a Visual Studio Professional subscription, and to users for whom you are paying for Azure Boards & Repos in an organization.
Box 2: Stakeholder
Assign Stakeholders to users with no license or subscriptions who need access to a limited set of features.
Note:
You assign users or groups of users to one of the following access levels:
Basic: provides access to most features
VS Enterprise: provides access to premium features
Stakeholders: provides partial access, can be assigned to unlimited users for free Reference:
https://docs.microsoft.com/en-us/azure/devops/organizations/security/access-levels?view=vsts