The exposure triangle includes shutter speed, aperture, and ISO
This is the exposure time, and the amount of time the shutter is open allowing how much light comes in. It can freeze an action. It's measured in fractions like 1/4 or 1/100, etc. A fast shutter speed will pause what's happening in time, but a slow one will make it blurry.
Larger aperture lets more light in and has a bigger opening, small aperture lets less light in and has a smaller opening. A small f stop will make the background blurry but the main object will be in focus, a large f stop will make the whole picture come into focus. Large aperture= small f-number= shallow(small) depth of field. Small Aperture= large f-number=deeper(large) depth of field. Measured in f numbers. Use a large aperture to freeze things in time or to have your background not in focus. Use small aperture for long distance shots like landscapes or sunsets.
ISO is how sensitive a film is to light or the sensitivity. The way it is measure doubles, it starts out at 100, 200,400,800,1600,3200,6400. 6400 is usually the furthest it goes. The higher the ISO is set to more noise there will be in the picture, the lower it is will make the picture more clear with much less noise. Higher ISO is usually used for when it is darker, lower ISO is when it it lighter. For example if it is sunny out then you would want to use a small ISO like 100 maybe 200. If it is dark out you want a higher ISO like 3200/6400. If you're in a gym or people are moving use 3200/6400 so it pauses the action in time.
The Exposure Triangle - Aperture, Shutter, ISO