title: Difference between Big-Theta and Big O notation in simple language
body: <p>While trying to understand the difference between <strong>Theta</strong> and <strong>O</strong> notation I came across the following statement :</p>
  
  <pre><code>The Theta-notation asymptotically bounds a function from above and below. When
  we have only an asymptotic upper bound, we use O-notation.
  </code></pre>
  
  <p>But I do not understand this. The book explains it mathematically, but it's too complex and gets really boring to read when I am really not understanding. </p>
  
  <p>Can anyone explain the difference between the two using <em>simple, yet powerful examples</em>. </p>