The exposure triangle consists of the three photography elements which are: ISO, Temperature, and shutter speed.
It is the exposure time to capture the light in the picture. It opens up to capture the entire picture with light. Shutter speed is measured in seconds, meaning 1/1000 is much faster than 1/30. Regular shutter speeds are 1/60. Anything under 1/60 you will have some blur to the picture without a tripod.
What is ISO or how to use ISO? Digital Photography Tutorial. Basic lesson for beginners
A hole in the camera that gives you a depth of field , wide or shallow depth of field depending on what you choose. Depending on the aperture setting you can either blur the main subject or the background of the main subject. The higher the number the smaller the hole.
Aperture - How to use it's editing tools
ISO is the sensitivity to the light captured in the lens. The higher ISO the more sensitive to light. The higher ISO it is depending on the time of, it will get grainy. High settings are typically used for nighttime, and vise versa.
Digital Photography - ISO
Photography Tutorial: White Balance Made Easy