Someone explain the "S" pattern stroke to me?

First off, I'm not a swimmer by trade, so be gentle with me. I taught myself freestyle a few years ago, with a reasonable amount of success. Took some lessons over the spring to tweak anything glaringly wrong, and even started swimming fast(er)--got to about 1:35/100 yd average, which is still slow, but fast for me!

So today, my boss, who's apparently a former college swimmer himself, was talking to me about my workout and asked "Do you do the S stroke?"

(Um. Not sure. What the heck is the S stroke?) He showed me how, as your hand comes past your body after it enters the water, you're supposed to make a slight S drawing with your hand/arm.

My main focus has been on keeping my elbows high through the stroke (someone on here once described it as imagining you had a board under your body and you couldn't straighten your arms, sort of like a surfboard). So, I'm pretty good at not straightening my arms under water and keeping my elbows high. But I've never really paid that much attention to whether or not I make an S shape. In fact, I think I've been purposefully trying to make one straight line after my hand enters the water. Boss said if you do the S pattern, you'll totally change the way you swim (i.e. faster). The coach I took lessons with never said anything about this.

Then again, it's hard to disagree with your boss/former swimmer extraordinaire.