Which index is what in CQ/CRX

> /repository/repository/index
Lucene Search Index for jcr:system (includes jcr:versionStorage)

> /repository/workspace/crx.default/index
Lucene Search Index for crx.default workspace

> /repository/workspace/crx.default/index*.tar
Tar PM Index for crx.default workspace

> /version/index {Version index offcourse}
Tar PM Index for version workspace

> /tarJournal/index*.tar
Tar PM Index for the cluster journal for Journal PM in 5.4

Thanks Andrew Khoury From Adobe for providing this information