google has very poor explanaition of it. I have already done it. I need to know how can explain it to someone who did not have very advanced mathematics.
Oh. That's a very different question from the one in the OP - it would have been better to ask this question first. Then I, who know nothing whatsoever about left invariant vector fields, would have not piped up at all. You need an expert like Drexel28 or maybe tonio to answer this.