Just because Snapchat mostly revolves around disappearing messages doesn't mean you always want those snaps to go away. In fact the company wants to help you do just the opposite -- it's launching Memories, a feature that saves both snaps and Stories for posterity. Once you've saved shots to Memories, you can create a Story from them or even link multiple Stories together. If you've been using Snapchat to document an epic vacation, you can share the whole thing as a giant collection of photos and videos. You should see the feature arrive sometime in the next month, and you'll get a chat when it's ready for you to use.
This naturally raises some privacy concerns, but Snapchat claims that it's doing its best to save you from uncomfortable situations. You can flag certain snaps as My Eyes Only so that friends won't stumble across something private. And while Snapchat does back up Memories, it'll only save the content that you either use to make a Story or flag as My Eyes Only. Your camera roll won't be exposed to the world, in other words.
The addition tackles one of the bigger gripes about Snapchat (keeping some of your snaps), but it's also a hedge against the competition. Rival apps like Facebook Moments are all about sharing shots from big occasions, and Snapchat doesn't want you jumping ship just because you don't have an easy way to relive major life events.