Big-O-Notation is used to measure and express the relative representation of the complexity of an algorithm:
Did you ever tried to understand why :
· Bubble Sort is O( n square )
· Quick Sort is O( n log n)
or you just remember it by heart and don’t know what’s hiding behind these names/values J
Below given are two best explanations I found in a quick search:
http://stackoverflow.com/questions/2307283/what-does-olog-n-mean-exactly
http://stackoverflow.com/questions/487258/plain-english-explanation-of-big-o/487278#487278
They both use example of Telephone Book and make it so simple to understand the whole thing.
If you understand the Telephone Book example then I guarantee you that you will be able to tell the performance of any algorithm in a quick moment without referring its documentation.
Namaste (Greetings)
Anugrah Atreya