Containers only separate Cookies and login data, to make you look towards the internet like multiple people.

Profiles on the other hand separate everything, as if you had two completely independent Firefox installations. Different browsing history, bookmarks, themes, extensions.

They work very well for allowing multiple people to all have their own Firefox, even though it's the same installation. But also really well for single-person use, for example I have a normal Profile for everyday browsing and then a webdev Profile, where I don't put in content/tracking blockers.

You can manage Profiles by typing "about:profiles" into the URL bar or with this: https://support.mozilla.org/en-US/kb/profile-manager-create-...