Parse was once the poster child for mobile back end as a service (MBaaS), and despite its recent acquisition by Facebook, it is still a viable, low-friction MBaaS for limited-volume consumer apps. On the plus side, it is well documented, it has good native client support, and it has a JavaScript client SDK based on Backbone.js. Parse also runs JavaScript code on the back end, which offers developers the option of an all-JavaScript application stack.
On the minus side, Parse is missing big pieces that are necessary for business apps, such as data integration, offline operation, and online/offline synchronization. At the same time, its pricing seems geared to lower-volume apps. If you happen to create the next viral hit, Parse will cost you plenty as the usage of your app picks up.