By Matt Wright
Resolution is the amount of pixels per square inch. Resolution effects the image when you degrade the resolution however when you make the resolution higher it doesn't change. However when you lower the resolution the image becomes much more pixelated. We would pick a lower resolution to make it a smaller image size. This could be helpful for storing files and if you were only showing the thumbnail of an image it would be a smaller file size. There is a link between the resolution and the file size. It is the larger the image resolution the higher the file size, this is because there a more pixels per square inch.
The color depth of a photo is how many colors it has. For example the photo above. 254 colors has a a wide array of different colors and makes the image looks smooth however at 8 colors it has a small range of colors. Or could be described as a 5 year old getting hold of photoshop.