compression question

Can you please explain compression - what is means, and how it works - why higher compression means more speed......thanks

your engine consists of cylinders(unless you drive a rotary car) and in these cylinders are pistons. the basic version of this answer is that as the cylinders fire, the piston moves up an down. how much the piston moves up determines your compression. the piston rises up and compresses the air/fuel mixture and then the cylinder fires forcing the piston back down.
now, higher compression can lead to higher horsepower because of the physics of internal combustion engines. the more you compress air in the cylinder the hotter it gets and the faster it burns; the faster the mixture in the cylinder burns, the faster it expands and the quicker the cylinder moves.
again this is the very simple version, hope it helps and if it doesnt(im not good at conveying concepts) go here:
www.howstuffworks.com
sift throught the automotive section til your hearts content.