how does a computer microphone work?

Answer 1

The same way all microphones work. There is a coil of wire around a magnetic core attached to a cone. The air waves vibrate the cone, which moves the wire coil back and forth across the magnet. The result is an AC electrical current that resembles the movement of the airwave vibration when viewed on an oscilloscope. This can in turn be captured and manipulated.

Answer 2

Analog signals are converted to digital.