This parameter will define how your camera is measuring the incoming light into the sensor in order to calculate a correct exposure. Usually, there are three main metering modes we can choose from:
Matrix metering: The camera is reading the whole sensor in order to calculate the correct exposure.
Center-weighted: The camera only uses the central area of the sensor to analyze the light and do the calculations.
Spot: The light is measured only in a small spot of the sensor (usually in the center).
Check my article about Metering modes in street photography for more information.