At what level does GIL limit execution in the interpreter or application?

GIL (Global Interpreter Lock) in Python restricts the execution of bytecode in the interpreter at the thread level within a single process. This means that at any given moment, only one thread can execute Python bytecode, even if the system has multiple cores. GIL does not restrict the execution of native code, such as I/O operations or calls to C extensions, which can run in parallel. Therefore, GIL limits parallelism at the thread level in the interpreter itself, not at the process or application level.