The GIL in Python is necessary because the CPython interpreter, which is written in C, is not thread-safe. Other implementations of Python, like Jython or IronPython, do not have a GIL and allow true multi-threading.

The GIL in Python does not allow multiple threads to execute Python bytecodes at the same time, which can limit the effectiveness of multi-threading when performing CPU-bound tasks. However, it does not affect I/O-bound tasks such as network requests or file operations.

The GIL is a mechanism in Python that ensures thread safety by only allowing one thread to execute Python code at a time. This makes it easier to write thread-safe code, but can hinder performance in CPU-bound scenarios.