Native code usually refers to code which is compiled to machine code (for the CPU it will run on) ahead of time, as opposed to code running in a byte code VM (possibly with JIT).

I would consider all of C, C++, Zig, Rust, Fortran etc to produce native binaries. While things like Cython exist, that wasn't what was used here (and for various reasons would likely still have more overhead than those I mentioned).

Native to the hardware platform.