MEMS microphone
A condenser microphone etched into silicon, small enough that a phone can carry three or four of them.
The principle is the same as in any condenser microphone: a thin diaphragm moves against a fixed backplate and changes the capacitance. The difference is that both parts are made with semiconductor processes and packaged together with a tiny ASIC that handles amplification and often the A/D conversion too. Knowles shipped the first commercial parts in the early 2000s.
Digital versions output PDM or I²S directly, which makes them immune to noise picked up on the circuit board. They survive reflow soldering, vary less from unit to unit than electret capsules, and have consequently taken over phones, earbuds and smart speakers. The noise floor is still higher than a proper studio mic's, but that is rarely where a phone is recording.