This affects how the camera evaluates the light in a given situation, and consequently what exposure settings your camera recommends.
Evaluative metering – meters the whole scene, the camera automatically sets the meter to suit the entire scene.
Partial metering – Takes a partial metering of the scene so if your background is much brighter than the subject you can meter just a small area.
Center Weighted – meters the center of the scene and then is averaged for the entire scene.
Spot Metering – meters for only a specific spot of the subject or scene.