>>3486545As others have said, the meter does indeed tell you if you're overexposed or underexposed.
You get overexposed shots by letting in too much light. This is done by having too slow of a shutter speed, too large of an aperture, or too high of an ISO. You underexpose with the opposite: too fast of a shutter speed, too small of an aperture, or too low of an ISO.
Shutter speed is how long you let light hit the sensor, communicated in (usually fractions of) seconds. For example, a shutter speed of 1/30 means the shutter is open for one thirtieth of a second. Slower shutter speeds result in motion appearing blurred, and too slow of a shutter speed will require using a tripod to hold the camera steady, as otherwise your shaking hands will blur the image. Conversely, a fast shutter speed will freeze motion, making it look like time has stopped.
Aperture is the size of the opening in the lens, aka the amount of light hitting the sensor. It's communicated in a fraction of the lens' focal length, shortened to just "f". For example, f/8 means the diameter of the opening is one eighth of the focal length of the lens. A bigger number means a smaller opening means less light. A wider aperture lets in more light, but this results is a shallower depth of field - this means that there's less of your photo in focus, meaning you need to be more accurate with your focus. A smaller aperture lets in less light, but increases the depth of field.
ISO is a carryover from film days, it's an arbitrary number that shows how sensitive the film is to light. The higher the number, the more sensitive to light. Since this number is arbitrary, it's good to know that twice the ISO value means twice the sensitivity to light. For example, 400 ISO is half as sensitive as 800 ISO, which is half as sensitive as 1600 ISO. A higher ISO value means that you don't need as long of a shutter speed or as wide of an aperture, but will result in lower picture quality due to increased visual noise.
