It's called Supersampling and basically gives the computer more options for what to render for any given pixel.
If you "render" at a higher resolution so that each final pixel is 4 pixels in the supersample then the computer gets 4 reference points for what color that pixel could be instead of just one. It can then average those 4 values and get a cleaner value for that final pixel.
When you have high contrast areas (black against white for example) the computer can pick a cleaner average between the two areas (shades of gray) instead of only choosing between white and black.
TrollErgoSum t1_jaa2qv9 wrote
Reply to ELI5: how does rendering a video game resolution above your monitor resolution make the picture more crisp? by ItsSnowingOutside
It's called Supersampling and basically gives the computer more options for what to render for any given pixel.
If you "render" at a higher resolution so that each final pixel is 4 pixels in the supersample then the computer gets 4 reference points for what color that pixel could be instead of just one. It can then average those 4 values and get a cleaner value for that final pixel.
When you have high contrast areas (black against white for example) the computer can pick a cleaner average between the two areas (shades of gray) instead of only choosing between white and black.