Thanks! The way Woo themes works (and I am sure many other themes) They have a main style sheet (style.css) and a stub, empty style sheet (style.css) that you use to override the main styling sheet. They suggest, with good cause, that you do not touch the style.css and make all your changes in the custom.css. They further suggest, that the method to accomplish this task is to copy and paste from the style.css into your custom.css, thus creating the override.
The only problem with this approach, is if your are like me, with a minimal and a slowly growing comprehension of CSS, targeting the exact code can be problematic. I often find 'leaks' of style that get through and come from another line of code. Using the Inspect Element, a feature of browsers, helps in this pursuit but obviously is not full proof.
The other issue I struggle with is the lineal inheritance nature of CSS. If a bit is farther down the file, it gets final say.
Thanks for taking the time to explain. Very gradually and grudgingly my brain is wrapping around this stuff.