Exposure

Shutter Speed is HOW much time you let light in, it's HOW FAST you take the image. 

Aperture  is HOW MUCH LIGHT you let into the camera. This is measured by how big the opening in the lens is.

ISO  is HOW SENSITIVE the sensor or film is to light. 

Balancing all 3 variables is the art of taking a good EXPOSURE or IMAGE.

What we are going:

Take 3 photos of the same item/person/place/angle...

Thank you to E. Snow for sharing this curriculum.