Difficulties while understanding Convolution I have just started convolution sum. I am able to do Mathematical convolution sum. But I am unable to make a figure of it in my mind. So I tried to go through the graphical convolution.
Below is the picture


I understand decomposed part but I don't understand that how each decomposed part is generating x[ 0 ]h[ n ],x[ 1 ]h[ n-1 ]....?

I guess a little help makes me to understand the Convolution sum.
Thanks
The convolution sum is 
\begin{equation}
y[n] = \sum_k x[k]h[n-k]
\end{equation}
If you take the term corresponding to $k=0$, the contribution is $x[0]h[n]$. Similarly the contribution of $k=1$ is $x[1]h[n-1]$. Here, $h[n]$ is delayed by $n=1$. Similarly you can see how each term of the sum contributes to overall sum. The sum is taken over values $k$ where $x[k] \neq 0$ because only those terms contribute to the sum.