In Microsoft's hybrid identity guidance, Azure AD Connect is the supported tool to bridge on-premises Active Directory Domain Services (AD DS) with Azure Active Directory (Azure AD). Microsoft Learn describes it plainly: "Azure AD Connect is Microsoft's tool for connecting on-premises directories to Azure AD." It "synchronizes user, group, and device objects" so cloud identities stay aligned with on-premises accounts and attributes. Azure AD Connect also supports multiple sign-in methods: "password hash synchronization, pass-through authentication, and federation integration." In other words, you can sync identities and choose how users authenticate to Microsoft Entra ID (Azure AD).
By contrast, Active Directory Federation Services (AD FS) is a federation service used for claims-based authentication; it does not perform directory synchronization. Azure Sentinel (now Microsoft Sentinel) is a cloud-native SIEM/SOAR and is unrelated to identity sync. Privileged Identity Management (PIM) is an identity governance feature for just-in-time privileged access; it does not synchronize identities. Therefore, in a hybrid identity model where the requirement is to sync identities between AD DS and Azure AD, the correct Microsoft-endorsed solution is Azure AD Connect, which "keeps identities in sync between on-premises directories and Azure AD."