Then how do you suppose the PCB connects to the motherboard? Magic?
Here is an image for your reference
This image shows the Sensor PCB unit along with Mic/LED Mounted in a Dell machine. The connector I mentioned is clearly labelled.Obviously, there is a corresponding connector on the Motherboard. Essentially its a 4pin USB connector for the Webcam (+5/TX/RX/Gnd), +5v/Gnd for the LED & TX/RX/Gnd for the MIC.
All laptops use something similar to the above, with the odd exception of seperate Mic units.