With it, you can open tabs in different 'containers', which have their own set of cookies, etc.. So, for example, you can be logged into two accounts for the same website, just in different containers, or keep all your shopping accounts in one container (and set those sites to always open in that container) to reduce tracking and targeting.
Ah. Interesting. For work I log in to a bunch of AWS accounts and I'm only able to do two at a time. One in a normal window and another in a private window. But I can't open a 3rd private window. So this will be the answer, I think.
About synchronization, one i've never seen is tabs, being able to open any tabs on one device to another. Maybe the clipboard too could also be useful to share link/text to another device...