Subtracting Values by Specific Row Number

Hi, I'm extremely new to Excel, and I have a simple question to ask.

I'm trying to make a formula that will take row specific values from two designated columns and subtract them, putting the result in a new column. I'm wondering how one would represent row number in a formula?
Here's what I mean: =J# - C#

Using =J(ROW()) - C(ROW()) didn't seem to work

thanks!