Light Meter

There are two general types of light meters reflected-light and incident-light.

Reflected-light meters measure the light reflected by the scene to be photographed. All in-camera meters are reflected-light meters.

Flash Meters, Mobile Cam Light Meters, Cine Meters,  Color Meters and Spectrometers,  Spot Meters,  Foot Candle and Lux Meters.

We've different types of reflective meters exist  Matrix or Evaluative Metering breaks a frame into zones.

It uses an average to judge exposure.