Pumping
    Lemma for Regular grammars is said to be the toughest idea to understand. Here I tried it
    in my own way to make you to understand the concept.

Pumping Lemma is a powerful tool to prove a language is
    not regular. The proof technique used here is Proof by Contradiction.
    ie., initially, in the proof, the language is considered as a regular language. The
    following table shows how and where pumping lemma used exactly:

The finite automata is simply a (virtual) machine and
    has no additional memory. It doesnot keep track of how many input symbols read. It just
    checks for whether the input string empties when reaching its final states.