With this feature enabled you can now backup all your camera originals in the cheapest cloud tier as an extra insurance.
Archive is a long-time cold-storage. Storing things in Archive costs about 8% of the hot storage we use for everyday used files. Files you are putting in Archive are files you want to have an extra security for but don't intend to use from the cloud on a daily basis, but you might need to recover if your house burns down.
To enable this function, have a look at this video:
If you need to share your originals between partners, you should use the regular storage.