Need help understanding summation notation problem...

So i'm doing some problems in my discrete math book. I ran into this little problem that has a solution in the appendix which I simply do not understand.

"Write each of 32-41 using summation or product notation.

32.

.

.

40. n + (n - 1) + (n - 2) + ... + 1

41."

The answer in the appendix says:

(n - i) where i = 0 is the lower limit and n-1 is the upper limit

I don't get this; that '... + 1' in the problem is throwing me off.

If you understand this, would you mind explaining this summation form to me.

Thank you.