A REST API allows you interact with Parse from anything that can send an HTTP request. The REST means “Representational State Transfer” that uses the four HTTP methods such as GET, POST, PUT and DELETE to execute different operations. These operations can be called by means of any the four verbs, using the actual URI as parameters for your operations.

Here are the example of what you can do with the REST API. A mobile website can get Parse data from Javascript, a webserver can display data from Parse on a website, you can upload large amounts of data that will used in a mobile app, you can download recent data to operate your own custom analytic, applications written in any programming language can interact with data on Parse and you can export all of your data if you no longer want to use Parse.