If your AirPods are in their charging case, the light automatically shows the charge status of the AirPods. If your AirPods aren't in their case, the light shows the charge status of the charging case itself.
If you have second-generation AirPods or a Wireless Charging Case, the light flashes for a few moments when you place the case on a wireless charging mat to indicate that charging has started, and then remains unlit for as long as you leave the it on the mat, whether the case is fully charged or not.
Green or amber status light
A green light indicates the AirPods or charging case are fully charged, while an amber light means there's less than one full charge left.
Flashing white status light
If the status light is flashing white, then your AirPods are ready to set up with a compatible device. You should see it when the button on the back of the case has been pressed.
Flashing amber status light
If the status light flashes amber, it's likely that you will need to set up your AirPods again before using them.