title: Big-O & Big-Theta: is a for loop O(1) time complexity?
body: <p>I have trouble understanding what Big-O and Big-Theta means exactly. Can someone please explain what it means illustratively?</p>
  
  <p>Given that n is a constant, is the for loop of O(1) time complexity for the worst case?</p>
  
  <p>Furthermore, is the worst case running time of the algorithm below O(n^2) since insertionSort is of O(n^2) complexity? If not, what is the time complexity of the below algorithm for the worst case?</p>
  
  <pre><code>void fnA(int[] array)
  {
     ArrayList a2 = new ArrayList&lt;Integer&gt;(array.length);
  
     for (int i=0; i&lt;n; i++) {
        a2.add(array[i]);
        insertionSort(a2);
     }
  }
  </code></pre>