The best wireless earbuds have worked the same way for decades now. Similar to big over-ear cans, there are drivers within each that transform the digital signal of any song you listen to into a mechanical vibration that pushes air into your ears as sound waves.
Things have moved on a little bit from this, courtesy of XMEMS with an additional tiny speaker that operates in tandem with the traditional driver to better separate the highs, mids and lows of any song you listen to, while offering better spatial audio.
