take the time to google what sync means !
Because you don't have your electronics sync, you won't see the same thing on each electronic. If you sync them, then when you delete an email on one electronic, it will be deleted on the others. It normally takes around 10 minutes when I delete on my pc before it shows up as delete on my cb.

By syncing you're also syncing your bookmarks and passwords, all electronics will show the same for both those but if you enjoy deleting emails on each electronic, trying to find which electronic you saved a bookmark to then continue not syncing your electronics.