What is a pixel?

A pixel is a physical point in an image where data is stored in the form of a colour, they are used to occupy screen space and when the colours are aligned specifically, an image is visually created. This is where pixel art comes from, it is where people manipulate pixels to create their own images. Other images types that manipulate pixel's are PNG's and JPEG's, A picture taken from the real world using a digital camera is made up of pixels, the quality of the image depends on the resolution of the image, an image with the resolution of 128x128 is going to have a significantly less amount of pixels in it whilst an image taken in high definition 1280 x 1080 is going to have far more pixels and thus the quality will be much better. The file size of a pixel is 1 bit or 1/8 of a byte.

An example of image quality using pixels.