Microsoft Graph Advanced Query Index Store explanation

Question

Hi all,

Is anyone able to explain how the Microsoft Graph engine uses an index store and what is meant by advanced queries using a separate index store?

Link to the relevant page on advanced queries: https://learn.microsoft.com/en-us/graph/aad-advanced-queries?tabs=powershell

I would be interested in a short explanation of how the flow/journey of a query is impacted/different with this separate index.

Thanks!