Glossary
Windows.edb
The ESE database that holds the Windows Search index from Windows Vista to Windows 10, stored in ProgramData\Microsoft\Search\Data\Applications\Windows.
Windows.edb is the Windows Search index file used from Windows Vista to Windows 10. It is an Extensible Storage Engine database, not an Exchange mailbox, although both use the .edb extension.
It lives in C:\ProgramData\Microsoft\Search\Data\Applications\Windows\ next to its MSS*.log transaction logs and MSS.chk checkpoint. Its main tables are SystemIndex_PropertyStore (one wide row per indexed item, SystemIndex_0A on Vista / 7) and the gather tables SystemIndex_Gthr and SystemIndex_GthrPth. A copy taken from a running system is usually in dirty shutdown state. See where it is stored and how to collect it.