Colour Depth
Image as pixels in binary
0 usually means a space, or blank to represnt gaps in images. 1 means what is seen so a black box or star.
Colour depth
The more colour depth, the bigger variety of colours making the image a better resolution but also the file size larger. The resolution depends on the amount of pixels there are, the higher the better,
Metadata
Metadata allows the computer to recreate the image from the binary data in the file. This contains height and width in pixels and the colour depth.