I assume it's this:

In Python, coroutines cannot yield from within another function call: if coroutine A calls function B, B cannot yield. In Lua, it's possible to yield a coroutine at any function depth: B can yield.

To implement something like this in a compiled language, you just need multiple stacks instead of the usual 1. Most architectures, such as x86, have a stack pointer register; when yielding a coroutine, just change the sp register to point to some other stack -- when resuming, restore the sp.

This is not a new concept. Pokémon on the gameboy did this for its UI fiber, for example.