An exposure meter is a device that determines how much light the film should receive to make a correctly exposed print that is neither too dark nor too light. You cannot actually touch the meter but in many cameras you can see what the meter is deciding through the viewfinder. In inexpensive cameras you cannot see what the meter is deciding through the viewfinder. It is best to have a camera that shows both what shutter speed and aperture are being considered as well as has the ability to override the shutter speed and aperture chosen by the meter. In inexpensive cameras the exposure meter is accurate about 60% of the time. In the most expensive cameras the exposure meter is accurate almost 100% of the time.