Dithering is a technique in digital graphics which uses patterns to create the illusion of greater color depth in situations with real or self-imposed color constraints. In historical applications of pixel art, dithering was often a necessity, as old platforms were limited in various ways. Due to the blurring and scaling inherent in CRT display technology, dithering patterns were less visible than they would be on modern displays. Some systems, like the Commodore 64, whose output used stretched or non-square pixels, gave dithering an entirely distinct look.
Now, any color limitations in our pixel art are self-imposed, and dithering displayed on modern screens does not convey the same effect. The things we find appealing in modern pixel art are different than they once were, but they are still influenced by techniques, including dithering, developed to cope with now obsolete restrictions.
See the full tutorial here: https://pixelparmesan.com/dithering-for-pixel-artists/(this website has a lot of good tutorials, take a look)
Cinco de Mayo