Why doesn't my laptop read my USB stick?

CD yes but USB no.

do you have any idea why?

USB stick defective, USB port defective, USB driver defective, … Choose something.

Does it work on other USB slots or on other PCs?

The stick could be defective, empty or the like. For a concrete answer, a more precise description of the problem is necessary.

Is the stick broken? I once did. Do other USB sticks work? Had to use the elimination process to test what was really wrong.

Try the stick on another port or computer. If it works there, either the driver or the port is broken; if not, then the stick is over the Jordan.

Have you checked the device manager?