Dithering: this is the process used to trick the human eye into seeing new colours and shades by slightly fading the already present pixels. If you look closely at the picture you can see the different colours even though that colour isn’t actually used, it is just a faded form of the surrounding colours.
Anti-aliasing: this is used to give picture a more smooth look so it becomes more appealing. When a computer doesn’t have enough resolution for the picture you can see the image has a blocky look around the border. Anti-aliasing blends the background colour with the colour of the border pixels to give it a more satisfying look.
Increase resolution (re-sampling): this involves changing the pixels dimensions but will result in loss of quality. It uses a process called interpolation which causes blurring when the size of the image is changed.