How were ancient instruments classified according to the hornbostel/sachs system? Name and briefly describe the four categories

The original Hornbostel/Sachs system had 4 categories:

1. Idiophones - Instruments that vibrate themselves such as a xylophone

2. Membranophones - Instruments that have a vibrating membrane such a as a drum.

3. Chordophones - Instruments with vibrating strings

4. Aerophones - Instruments which incorporate vibration of air.