x Σ times x ^? Please answer.

Hi Dragon Slayer,

I see you have found a new method for making 'legitimate' posts.  I hope that you learn something from it. 

Anyway, I have learned something - I have never written this in LaTex before!

By the way, LaTex is pronounced LayTec

$$\\\sum \quad \mbox{This is the Greek letter 'capital sigma' and it means 'sum of'}\\\\ \sum\limits_{n=1}^5\;(n^2-1)\\\\ =(1^2-1)+(2^2-1)+(3^2-1)+(4^2-1)+(5^2-1)\\\\ =1+3+8+15+24\\\\ =51\\\\ \mbox{You see how I have replaced the n with the numbers from 1 to 5 and added them all together?}$$

Oh sorry, I didn't even notice the original question.  This was a puzzle question.

I think that Aziz answered it a day or 2 ago.  I think it was Aziz, maybe it was Ninja but I don't think so. 

It was a really good answer too.  

What does Σ mean?

Can you please explain it to me please?