my chevy optra

I recently bought a chevy optra LS 2004 and Ive been told that i needs a new polycog belt Im not even sure what that is or what it does, can someone help me?

Also Im experiencing a new problem, my car seams to hesitate when Im accelerating almost like the gears are slipping or something, what could that be?

Hi Gidget. I am assuming you have repaired your car by now. I am also having stumble under load. It's throwing dtc po341, cam position sensor input to low or too high. How did you repair your's? The first question is referring to your timing belt.