Nim is a "language" that people can use to "code". It's a way for smart people to tell computers what to do in a special way.
It's called "Nim" because it's named after the game of Nim - a game where you have a bunch of sticks and you take turns removing one, two, or three sticks until there are none left.
Nim is like a game, but instead of playing with sticks, you play with words in a special code. People who know how to speak Nim can tell the computer what to do with these special code words.
Nim is special because it's easy for people to write code in a way that makes sense to them, and it also makes it easy to read the code later on.
Nim is like a secret language that only computers can understand, and if you know how to speak Nim, you can tell a computer what to do!