Source of Authority (SoA) describes where the user is primarily defined. This can be classified in to four categories. A user can be defined in,
1) Azure Active Directory
This is a native cloud user account also known a member.
2) External Azure Active Directory
Invited user from another azure tenant. If you invite a user from another tenant to your tenant, the user's SoA will be External Azure Active Directory.
3) Microsoft Account
A person who creates the subscription (Subscription owner) with a Microsoft account (live, hotmail etc) will have the SoA of Microsoft Account.
4) Local Active Directory
Synchronized user accounts with an on-premises Active directory will have the SoA of Local Active Directory.
1) Azure Active Directory
This is a native cloud user account also known a member.
2) External Azure Active Directory
Invited user from another azure tenant. If you invite a user from another tenant to your tenant, the user's SoA will be External Azure Active Directory.
3) Microsoft Account
A person who creates the subscription (Subscription owner) with a Microsoft account (live, hotmail etc) will have the SoA of Microsoft Account.
4) Local Active Directory
Synchronized user accounts with an on-premises Active directory will have the SoA of Local Active Directory.