Before high-resolution screens were available, those with lower resolutions required the use of font files that went through a hinting process.

Digital fonts are files with glyphs as vector contours shaped by the designer on type design applications. On lower-resolution screens, they are rendered by being adapted into bitmap fonts on pixel grids.
Hinting is about giving instructions to each pixel’s position in lower resolution situations, ensuring a rendering that is as close as possible to the original design.