These days, we're blessed with incredibly powerful graphics cards, with oodles of fast temporary RAM to store massively detailed textures and colour information. But it wasn't always so easy. Ever wondered how old computers, with basically zero onboard memory, actually created genuinely complex and colourful on-screen graphics?
The iBookGuy on YouTube has a great introductory video on the topic, talking about the limitations of computer systems from the early '80s and early gaming consoles like the NES -- including the fact that most computers didn't even have enough memory to display 256 different colours on the screen, let alone the millions we're all used to these days.
Because of these hardware issues, incredibly clever workarounds were necessary. When you only had 16kB of memory to work with, and displaying a 320x200pixel screen with monochrome information (white pixels on or off, basically, for a black-and-white screen) would cost you 8kB in the first place, you had to use smart hacks like the Commodore 64's colour cells -- basically dividing the screen up into segments of eight pixels, and using a single byte of information to define those cells' background and foreground colours. Sounds like magic, right? That's only the start.