To take advantage of the feature, users need to tap and hold the bookmark icon, located below a picture. Doing so allows one to save an image to a pre-made collection or folder. Users can create a new collection on the fly immediately after saving a post. Alternatively, it’s also possible to make a collection from an older saved image by tapping on the plus icon located at the top right corner. It’s possible to add previously saved images to a collection after the fact.
Collections can be found under the same tab where users can currently find their saved posts. Like with saved images, only the user doing the saving can see collections.
— Instagram (@instagram) April 17, 2017
According to Instagram, it added this feature because 64 percent of users saved at least one photo since the feature was added. The folder tool is not necessarily all that new as the collection feature is an utility that photo collecting apps like Pinterest have used in the past.
The collections feature is a good way of keeping photos organized and keeping track of the posts that need to be remembered.