isn't that the same as the Person profiles in Chrome?

No, Profiles are an entirely separate feature that Firefox also has. Setting up separate profiles for every major site could achieve something similar, but that would obviously be unimaginably inconvenient. Containers are like sandboxed virtual browser instances that nullify most methods of cross-site tracking, while also enabling you to conveniently stay logged in to all of your sites. Switching between the containers is seamless, and does not require any conscious user action apart from initially setting them up. Plus, the real kicker is using Temporary Containers as the default setting for new tabs, which can make it as if every Google search or inconsequential browsing session is done in a Private Window instance. This means there's no way in terms of cookies and trackers for Google to obtain cumulative data about your searches and browsing habits, but you can safely keep local records of your history if you want. There's no way to achieve any of this in Chrome with anything approaching the same level of simplicity or convenience.

How so? This is exactly what personal profiles do. Keeping a separate cookie jar, local storage, history, extensions. Basically only the browser version and OS related stuff is left to track you. Ok, except if Google tracks browser usage directly. I've been using separate profile for each of the evil websites I have to use, no cookie leaking.

I've edited the comment to clarify, but you're right that they're functionally similar. I was talking mainly in terms of user experience, though. Setting up multiple separate profiles with much the same options and extensions, and then having to actively fire them up for every time you want to use a major site that also employs trackers seems massively inconvenient and redundant to me. With containers, mapping specific sites to specific containers that first time is all you have to do. Containers also share local storage, history, and extensions with the rest of the browser, which is a blessing, as there's no need to install the same set of extensions five different times for as many different profiles, for no added security or privacy benefit whatsoever, and you can access local data in consolidated form, without having to deal with them being fragmented across multiple profiles.

Firefox splits the functionality of Chrome profiles into two different things:

Profiles contain all your settings, history, bookmarks, themes, sync settings, etc. They’re stored in a folder on disk. It’s kinda a hassle to switch between them.

Containers isolate cookies (and other stuff?) within a single tab or group of tabs. It lets you run a specific website or set of websites in isolation from your other browsing activity. This has security benefits, but is also great for logging into the same service with multiple accounts simultaneously.

I was initially annoyed by Firefox profiles because they’re clunkier than Chrome accounts, but was very happy when I figured out that Firefox Containers gave me the isolation benefits I was actually looking for, with some real improvements over Chrome.

I do wish there was a sync option, since I have to setup the containers and rules for opening websites in those containers every time from scratch.

You can configure the addon to open specific websites in different containers, and it all works seamlessly.

Except of course, syncing container rule settings across Firefox sync devices.