title: What exactly is NoSQL?
body: <p>What exactly is NoSQL? Is it database systems that only work with {key:value} pairs?</p>
  
  <p>As far as I know <code>MemCache</code> is one of such database systems, am I right?</p>
  
  <p>What other popular NoSQL databases are there and where exactly are they useful?</p>
  
  <p>Thanks, Boda Cydo.</p>