title: What is an example of a non-relational database? Where/how are they used?
body: <p>I have been working with relational databases for sometime, but it only recently occurred to me that there must be other types of databases that are <strong>non</strong>-relational.</p>
  
  <p>What are some examples of non-relational databases, and where/how are they used in the real world?  Why would you choose to use a non-relational database over relational databases?</p>
  
  <p><strong>Edit</strong>:  Two other similar questions have been mentioned in the answers:</p>
  
  <ul>
  <li><a href="https://stackoverflow.com/questions/51027/database-system-that-is-not-relational">Database system that is not relational.</a></li>
  <li><a href="https://stackoverflow.com/questions/37823/good-reasons-not-to-use-a-relational-database">Good reasons NOT to use a relational database?</a></li>
  </ul>