So, at the risk of asking a monumentally obvious query, what are the channels/gutters/padding bits at either side of a webpage called? e.g. on stuff.co.nz, the bits where the ads appear on the right and left hand sides of the actual site/"news"/latest celebrity gossip.

I'm trying to put together a *very* basic website using Squarespace's Native theme/template. Generally it looks good, but a little stark/severe at the moment. I was hoping to put a subtle image or colour in the channels so the whole screen isn't white, but my google fu has completely failed me. Hard to google instructions when you don't know what you're instructing.