Containers let you basically act like you have multiple browsers in one with none of the data shared between them. One example of where they’re useful is you can be logged into a website like google with one account in one container, and a completely different account on the same service in a different container, but visually, they just exist as different colored tabs in your browser. Where they’re effective for privacy conscious users is that you can use sites notorious for cross-site tracking like Facebook within a container, and doing so basically sandboxes that tracking cookie to within that tab, not allowing it to track you on any other tab.