With eSync setup you will see tracking tables generated for almost every table in your site's database. This KB explains the purpose of them.
The purpose of tracking tables is as you might expect, to track actions taken on content for the purposes of eSync. This information in the tracking tables allows eSync to make decisions about whether to move, delete, or update content to on the receiving end of a sync.
You can see when a row was last changed by the last_changed_datetime field. This is helpful when you want to see when a row was changed in comparison to the corresponding row of the database you are syncing to. This can show which side the content was edited on most recently which can explain why a particular row isn't syncing as expected.
Another helpful field in the tracking tables is the sync_row_is_tombstone. This tells you if content had been deleted at one point. If you see sync_row_is_tombstone set to 1 that indicates the content was deleted and cannot be recreated which explains why you cannot use sync as a restore method.