Last month Engadget announced that Instagram was working on a new feature called the "Archive". The Archive lets you hide your old photo without ever deleting them.
If you go into the “...” menu on a photo, where you’d normally see options like edit and delete, there’ll now be an option to archive the image placed right on top. Hitting that button will send the photo to a private gallery — your archive — where only you can see it.
The feature is slightly reminiscent of Snapchat's Memories, launched in 2016 which holds photos and videos for posterity, but doesn't share with friends.
The only difference here is that the photo cannot be added directly to the Archive folder- the photo has to be public and then it can be added to the Archives folder. For this reason, the feature will probably be more used as actual archives section, where you store photos which you never make public again in the near future.