title: NP-Complete VS NP-Hard
body: <p>I am trying to understand the difference between NP-Complete and NP-Hard. </p>
  
  <p>Below is my understanding </p>
  
  <blockquote>
    <p>An NP-Hard problem is one that is not solvable in polynomial time but can be verified in polynomial time.<br>
    An NP-Complete problem is one that is in NP and is also NP-Hard. </p>
  </blockquote>
  
  <p>Is the above definition correct? If so, What about problems not In NP but NP-Hard. Wouldn't they be harder than NP-Complete problem, say they can only be solved and verified in exponential time? </p>