MongoDB is a widely used, powerful NoSQL database. It allows you to store your data inside documents; a mutable, dictionary-like, object-like structure where your data may be stored without you worrying about things such as "is my data normalized to the third normal form?" or "do I have to create another table to store my relation?", and others.
MongoDB documents are actually BSON documents, a superset of JSON with extended data type support. If you know how to handle JSON documents, you should have no problem.
If JSON means nothing to you, just take a look at http://www.w3schools.com/json/.
Let's install MongoDB locally in order to try out some examples:
sudo apt-get install mongodb
Now, from console, type:
You'll enter the MongoDB ...