"Three DBAs walk into a NoSQL bar. A little while later they walk out because they couldn't find a table."
For our examples in this book, we will use a service in a cloud called MongoHQ. It's the most powerful platform for MongoDB hosting. Apart from providing one of the best MongoDB hosting solutions, they recently released a beta REST API for accessing their services. This is quite interesting for using in mobile clients, as accessing directly a MongoDB server is not the easiest of tasks.
MongoDB's main difference from "classical" relational databases is that instead of storing data in tables, MongoDB stores structured data as JSON-like documents with dynamic schemas (MongoDB calls the format BSON), making the integration of data in certain types of applications easier and faster.
The nice part about it is if you are not sure beforehand on what your data will look like, the document-type databases are a weapon of choice. You can change the structure with ease almost on the fly; you don't need to run any migration scripts. This greatly simplifies development in the early stages and/or the startup phase.