Filming & Production
Exposure triangle
Also called: aperture shutter ISO
Aperture sets how wide the lens opens, which also sets depth of field. Shutter speed sets how long each frame is exposed, which also sets how motion blurs. ISO sets the gain applied to the signal, which also sets how much noise you see. All three make the picture brighter, and each charges a different price for it.
Video removes most of the flexibility. Shutter is effectively locked at roughly double the frame rate to keep motion looking normal, so you are left with aperture, ISO and controlling the light itself, which is why ND filters end up on every serious camera. Beginners solve every exposure problem with ISO and then wonder where the noise came from.