Yeah, pitch is up/down. Yaw is left/right. (Roll is tilt from side to side). Terminology is based on aeronautics-n-stuff. They represent your 3d angle/orientation in space with the different 2d angles (since jka assumes you're straight up and down, roll isn't used I think... except maybe for tiefighters).
cl_yawspeed is how fast left/right commands increase/decrease your yaw... not sure what cl stands for... maybe something about constant something or something logic. I'm assuming m is for mouse because your questions all seem to be mouse releated
Only time I've heard of dpi is dots per inch for resolutions. Google tells me it can have something to do with your mouse's specs or something about the movement of the mouse.
As for my settings I yews base settings for pretty much everything... especially since when I mess with some of them my entire cfg gets corrupted and I have to start from scratch :/