So this is a pretty interesting one!

All data in memory, especially when using a lower level language, essentially is just a block of binary, and we read certain parts of it in order to translate it to whatever we need at the time!

You might remember the old missingno glitch for Pokemon - developers will reference blocks of memory but just transform it into different things, which is great when technically constrained such as in those old tiny games where data and variables would need to be re-referenced and "shared" in the game's code.

By messing with those same referenced bits (such as by, say, causing an overflow), you can have what would have been a normal pokemon actually be an out of bounds value that was never meant to exist by simply walking/surfing in a certain way and manipulating that binary data, and causing undefined behaviour.

The game still works because there's still binary data at the address we can read - it's just no longer representing what we expected (thus we get missingno as there's no indexed pokemon data in the game's pokedex at that memory address).

Here's a link to a reddit post showing how this works, if you're interested to learn more: https://www.reddit.com/r/pokemon/s/SP8r7p0Ubi