Exposure Triangle
Shutter Speed- Aperture- ISO
Shutter Speed
The shutter speed is what determines how long the shutter remains open as the picture is being taken.
How To Set Shutter Speed for DSLR Video
Aperture
Aperture is the amount of light being let into the camera.
Video Basics: Aperture
ISO
ISO is the level of sensitivity of your camera to available light.
A Simple Explanation of ISO for Digital Photography and Video