From my understanding, it provided services that you would have to create from scratch in your own infrastructure that would be a significant undertaking. For instance, push notification in iOS is a bit of a nuisance if your app really doesn't rely on a complex server back end, but you would like to still add push notifications. Parse did this portion for you, so you could focus on the product. I could be wrong though, I looked at it a year ago, and my memory isn't what it used to be.