Many NoSQL databases exist in the market today, but MongoDB, by the company with the same name (http://www.mongodb.org/), is the most popular among them. An important distinction between relational and NoSQL databases is that NoSQL databases are schema-less; this means you don't have to define the tables before inserting data. This in itself, of course, adds a lot to the flexibility and agility in the use of these databases; for example, adding a new field no longer means that you have to alter the table and run the SQL update commands. As there are no SQL queries to be used here, all the data retrieval happens via standard CRUD calls (create, read, update, and delete). In MongoDB, this is known as insert, find, update, and remove. MongoDB presents itself as an open source, distributed, document-oriented database: each data record is actually a document. A table is called a collection in MongoDB. Documents are stored in a JSON-like format called Binary JSON (BSON...