GDScript is not compiled to native binaries ahead of time (AOT). It is not compiled just-in-time (JIT) either. In short, it's an interpreted language, similar to Python in how it is run.
However, exporting your game will, by default, convert your
.gd scripts to
.gdc bytecode (resulting in slightly faster loading of the game, in some cases). Exporting in release mode will give large performance improvements because of the lack of run-time checks that are only helpful for debugging. You can sometimes notice a performance improvement of 300% by exporting in release mode, in contrast to running from the editor.