Overview

Entra ID (formerly Azure AD) - PAAS
Exchange Online - PAAS (Admin side) & SAAS (User side)
Sharepoint Online - Paas (Admin side) & SAAS (User side)
Intune (MDM) - Mobile Device Management, Across multiple OSs (Android, Windows, etc)
SCCM (Older) - Windows only, Group Policy
Main system - Microsoft 365 - Sits on top of Azure
Microsoft 365 - PAAS & SAAS
Azure - IAAS
Microsoft Cloud
Blue - Microsoft 365
Red - Azure Infrastructure
Purple - Microsoft 365 & Azure both share Entra ID (directory services)
Cloud Sync - SSO logs users in via on-prem D.C, and Entra ID via cloud (syncs out but not in)
Entra Connect server (formerly Azure AD Connect) - link on-premise with cloud services
Entra ID Sync (light weight version)