Subpixel rendering
Exploiting the fact that each pixel consists of three coloured stripes, and thereby tripling the horizontal resolution for text.
An LCD pixel is really a red, a green and a blue bar side by side. By lighting them to different degrees you can place an edge with one-third-pixel precision. The eye reads this as sharper text, even though magnification reveals coloured fringes.
Microsoft's ClearType made the technique widespread around 2000. It has two weaknesses: it assumes a particular subpixel order, so a rotated display or an OLED with different geometry gives wrong results, and it does not work at all when text is rendered onto a transparent surface. High-resolution displays have reduced the benefit, and macOS dropped the technique in 2018.