Saws are the ones that go from zero to whatever and drop off. Ramps are the ones that increase and then drop to zero. Think of it as if you're coming from the left. Saw is the one that would stop you. Ramp is the one that would make you do jumps.
There are minor audible differences... but very minor. I mean, I don't actually know... I'm just going by the Minimoog. The ramp and saw sound slightly different in comparison, but almost identical without comparison. The important difference is when they're treated as modulation sources. A ramp and a saw sound completely different in an LFO. And that's the most important part.
P.S. I recently did a shitload of videos for video education site, which are coming out soon. In them I discover that a lot of vintage synths portray their saws as ramps and ramps as saws! I can't remember which, though. Also, square waves are not square on a lot of synths.
"I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question." -Charles Babbage
"Unity and Mediocrity are forever in bed together." -Zane W. http://www.youtube.com/automaticgainsay