It’s just compile time code execution.
The difference between those macros („procedural macros“) and regular macros is that while regular macros are pretty much only templated code that is unfolded, proc macros contain code that is run at compile time, so they are more powerful but also more dangerous from a security perspective as you would expect just compiling a program to be safe.
Also: is copy pasting ChatGPT answers a thing now even when you, as you said, don’t even know what it means??
And your typo fix kickstarts 10 workflows, downloading gigabytes of data and running endless tests.
Depending on the size of the project, this may be an environmental concern.