Azure AD has five different editions. Azure AD free edition is the default edition for any Azure and Office 365 subscription. Basic and Premium versions are available through the Microsoft Enterprise Agreement, the Open Volume License program, and the Cloud Solution Providers program. Microsoft EMS E3 and E5 licenses also come with Azure AD Premium editions. More information about these editions can be found at https://docs.microsoft.com/en-us/azure/active-directory/fundamentals/active-directory-get-started-premium.