What is aperture in photography?

The largest camera aperture is f stop 1.4, which lets the most amount of light into the camera.

Aperture priority lets you set the aperture you want and the camera sets the shutter speed for you. You use it when you want to control depth of field. Shutter priority lets you set the shutter speed...

The hole that lets in light in the shutter that creates your image.

Just like with any other art, it's about capturing beauty and bringing an artist's emotions and vision of the world out in a tangible media to be enjoyed.