In Azure Active Directory (Azure AD), you can create complex attribute-based rules to enable dynamic memberships for groups. Dynamic group membership reduces the administrative overhead of adding and removing users.
When any attributes of a user or device change, the system evaluates all dynamic group rules in a directory to see if the change would trigger any group adds or removes. If a user or device satisfies a rule on a group, they are added as a member of that group. If they no longer satisfy the rule, they are removed.
Reference:
https://docs.microsoft.com/en-us/azure/active-directory/users-groups-roles/groups-dynamic-membership