Portals and centers are User friendly GUI tools available for organization which running in the cloud(Azure) and will help in providing access, managing users and security.

• Power BI Admin Portal: This portal helps to manage User metrics, Users, Audit logs and  tenant SETTINGS and Premium capacity settings in organization.
• Office 365 Admin Center: This center enables to manage users, configure, setup, groups and licensing, monitoring activities and see descriptive reports.
• Office 365 Security & Compliance Center: This center will help to protect data by providing right roles & permissions to users and also COMPLY with legal by following regulatory standards.
• Azure Active Directory (AAD) in the Azure portal: AAD is basically to manage IDENTITY and  Access Management which helps organization to provide maintain Single SIGN On(SSO) id for their users. In this portal, admin can add, remove, restrict the access for users (or) user groups (or) security groups in the organization.
• Powershell Cmdlets Administrative APIs & SDK: This part of azure portal, where admin can manage the users, user groups, security groups, etc.. by command-lets instead of GUI.