If you’re new to photography, the graphic below helps to explain your camera’s metering modes.
Segment (or Evaluative): the meter calculates exposure based on readings from different areas. The current exposure information is compared with evaluative metering data stored in the camera. The most appropriate exposure is calculated in an instant.
Partial: the meter takes a reading from about 10% of the overall image. This can be very helpful when the subject is mostly light or dark.
Spot: similar to partial, but reading taken from only a central 2 or 3% of the image area. Accurate if used properly.
Centre-weighted average: the meter takes a reading from the whole scene, but gives much more importance to the central area.