Containers are different from profiles. Firefox has both. Containers are within a single profile (and thus can be opened within the same window) and let you do

Containers are different from profiles. Firefox has both. Containers are within a single profile (and thus can be opened within the same window) and let you do things like ensure certain sites get opened in certain containers only (at least, I think that feature is still there). Containers are a first class feature as well, however there is an addon for supplementing their behavior. Firefox also has profiles (about:profiles) but with less UI around it so it's annoying to use.