What "Native functions" means or refers to, in a programming language?

I am reading the book "Crafting Interpreters" by Robert Nystrom where he has a list on Github with all Lox's implementations that other readers have done in other languages. I saw that one of that list says that it does not have native functions and I would like to know what it means about that?

https://github.com/munificent/craftinginterpreters/wiki/Lox-Implementations

CodePudding user response：

Native Function Definition, from the book "Crafting Interpreters" by Robert Nystrom

http://craftinginterpreters.com/calls-and-functions.html#native-functions