Product , catalogs etc both staged and online we have in Hybris...If we want show online the staged one we do synchronization but why we need staged products or catalogs?
Modifications of - Content, Product, Media,... - are made first in the staged catalog.
When changes/modifications are tested/approved and you are satisfied then you publish them to be available online to your users by synchronizing staged catalog to the online catalog.
Imagine if you have one single catalog, your users will be able to see unapproved and untested changes immediately, that's will increase the amount of risks and errors significantly.