the exposure triangle is simply the relationship between your iSO shutter speed and aperture these three components work together to create an actual exposure or photography
ISO
in digital photography iso measure the sensivity of the image sensor the same principles apply as in photography the lower the number the less senstive your camera is to light and the finer the grain by choosing a higher iso you can use a faster shutter to freeze the movement
Shutter speed
in photography shutter speed or exposure time is the lenght of time when the film or digital sensor inside the camera is exposed to light also when a camera shutter is open when taking a photography the amount of light a reached the film on image sensor is propotional to the exposure time
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane.