With the WordPress + Office 365 plugin you can basically two supported authentication scenarios:
Using one of the two scenarios, you can now decided whether authentication (for Office 365 / Azure AD users) is required for all users that are readers of your posts and pages (= intranet) or only for authors who access the WordPress backend e.g. the authors and editors of those posts and pages (= internet).
Obviously, in an intranet scenario – which is the default scenario – you would want all users to have authenticated successfully with your Office 365 tenant’s Azure Active Directory, as most content is likely to be at least classified for internal use only.
However, to accomodate for scenarios where such authentication would not be required and you only want the authors to use the Azure Active Directory integration you should select the internet scenario.
Launch the WordPress + Office 365 wizard by navigating to WordPress Admin, go to the plugins page and click Configuration. Select the Single Sign-on tab and use the drop down labelled Authentication scenario to choose either the intranet or the internet scenario.