Instagram has introduced a new feature, whereby users can include a post or picture in their private collection. Usually Instagram posts are self-disappearing and you and others cannot see it after sometime.
Now Instagram users can click a bookmark icon on the left and save post in their private collection, this way they can see it some other time.
Instagram has introduced this feature for both iOS and Android. If you are using Instagram version 10.2, then you can easily access this feature.