Multithreading in Python refers to the mechanism of dividing the main task into more than one sub-tasks and executing them in an overlapping manner, which makes the execution faster compared to single-threaded programs. A thread is a unit of execution within a process, and multithreading is a way of achieving multitasking. In Python, the threading module provides a simple and intuitive API for spawning multiple threads in a program.

However, its important to note that Python has a Global Interpreter Lock (GIL) that limits one thread to run at a time, even if the machine contains multiple processors. This means that Pythons multithreading module doesnt behave the same way as in other languages such as C++ or Java.

Despite this limitation, multithreading can still be useful in Python for tasks that can be broken down into smaller subtasks, which can then each be given to a thread to be completed. Additionally, Python provides other ways of achieving concurrency, such as multiprocessing, which allows for true parallelism by running multiple processes simultaneously.