The Exchange Hybrid Deployment feature allows for the co-existence of Exchange mailboxes both on-premises and in Azure by ...

The Exchange Hybrid Deployment feature allows for the co-existence of Exchange mailboxes both on-premises and in Azure by synchronizing a specific set of attributes from Azure AD back into your on-premises directory.

The specific set of attributes is determined based on the version of Exchange installed in your on-premises environment.

{0} about the attributes written in an Exchange Hybrid deployment.