A driver in this context is a piece of software that lets the operating system know how to talk to the hardware. That is, it takes requests from the operating system to do things, and turns them into instructions that the physical device understands, and turns the returning response into messages that the operating system can interpret.
If you don't have one, the operating system can try to issue all of the instructions that it wants for noise to be produced, and the hardware won't get the message.
Cheers,
Ben