Aperture

Aperture is how big the hole is where the light goes through.
The smaller the number the bigger the hole and the larger the number
the smaller the hole.

The shorter the depth of field, the background will be blurry.
The deeper the depth of field, the background will stay in focus.
- f2 is a larger aperture
- f 22 would be the smaller aperture and will not blur the background.