A tool that synchronizes identities between on-premises Active Directory and Microsoft Entra ID, enabling hybrid identity scenarios. It supports Password Hash Sync (PHS), Pass-through Authentication (PTA), and federation (ADFS).
On AZ-305 you design the hybrid identity strategy: PHS is the simplest option and the one Microsoft recommends (least infrastructure). PTA validates against on-premises AD in real time. ADFS is reserved for advanced federation requirements; Microsoft recommends migrating from ADFS to cloud authentication when possible.
Microsoft Entra Connect (Azure AD Connect) is a concept that can show up on the exam. Check the full guide to see it in context.