A nice intuitive approach to data separation, which simplifies my work-from-home process greatly by allowing me to separate all my work logins from all my personal logins, and even run them side-by-side in separate tabs. It can also be augmented by other addons (Temporary Containers) to open multiple separate sessions on a site at once.

Many workflows that other people would pull out a whole new browser for just require opening a tab in a different container.

This is one of those "bread and butter" addons that does something super basic but you wonder why it isn't the norm in every browser.