title: what is order of complexity in Big O notation?
body: <p><strong>Question</strong></p>
  
  <p>Hi I am trying to understand what order of complexity in terms of Big O notation is. I have read many articles and am yet to find anything explaining exactly 'order of complexity', even on the useful descriptions of Big O on here.</p>
  
  <p><strong>What I already understand about big O</strong></p>
  
  <p>The part which I already understand. about Big O notation is that we are measuring the time and space complexity of an algorithm in terms of the growth of input size n. I also understand that certain sorting methods have best, worst and average scenarios for Big O such as O(n) ,O(n^2) etc and the n is input size (number of elements to be sorted).</p>
  
  <p>Any simple definitions or examples would be greatly appreciated thanks.   </p>