A hybrid SharePoint deployment is a link between a SharePoint Server farm and Office 365. It also can be called as a redirection. It does not create a replica.
When you have established this link (redirection), you can configure integrated functionality between services and features such as Search, Follow, and user profiles.
References:
https://learn.microsoft.com/en-us/sharepoint/hybrid/sharepoint-hybrid-sites-and-search
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