Exposure in photography describes the exact amount of light that comes from outside to strikes the sensor. There are three types of variables that help to control this setting, namely ISO, shutter speed and aperture.
These modifications are essential since there is currently no electronic sensor developed in such a way that can capture the entire continuum of light intensities the eye responds to.
Through learning how to expose an image accurately, you will gain that ability to take pictures of the perfect lights or brightness, both in shadows and in highlights, along with finer details.