What is the difference between a relational database and a non-relational database?

The current mainstream relational databases are Oracle, DB2, Microsoft SQL Server, Microsoft Access, MySQL, and more.

Non-relational databases have NOSQL, Cloudant.

NoSQL and relational database comparisons?
Advantages:
1) Cost: NoSQL databases are simple and easy to deploy, basically open source software, and do not need to spend a lot of money to buy using Oracle, compared to the relational database is cheaper than the price.
2) query speed: NoSQL database stores data in cache, relational database stores data on hard disk, natural query speed is far less than NoSQL database.
3) format for storing data: NoSQL storage formats are key,value forms, document forms, picture forms, and so on, so you can store the underlying types and objects or collections, and the database supports only the underlying types.
4) Extensibility: The limitations of a relational database with a multi-table query mechanism like join cause the extension to be difficult.
Disadvantages:
1) Maintenance of tools and information is limited, because NoSQL is a new technology, not with the relational database 10几 years of technology in the same breath.
2) does not provide support for SQL, if it does not support industry standards such as SQL, will generate a certain user's learning and use costs.
3) does not provide a relational database to deal with things.

What is the difference between a relational database and a non-relational database?