The threading module: This module provides a way to create and manage threads in Python.

The Thread class: This class represents a thread of execution in Python.

The Lock class: This class provides a way to synchronize access to a shared resource, such as a variable, between multiple threads.

The Semaphore class: This class provides a way to limit the number of threads that can access a shared resource simultaneously.

The RLock class: This class provides a reentrant lock, which can be acquired multiple times by the same thread.

The Condition class: This class provides a way to wait for a specific condition to be met before continuing execution of a thread.

The Event class: This class provides a way to signal between threads, allowing one thread to wait for an event to be set by another thread.

The Barrier class: This class provides a way to synchronize the execution of multiple threads at a specific point.

The Queue class: This class provides a thread-safe queue for exchanging data between threads.

The Pool class: This class provides a way to execute a function on multiple inputs concurrently using a pool of worker threads.

The concurrent.futures module: This module provides a high-level interface for asynchronously executing functions using threads or processes.

The GIL (Global Interpreter Lock): It is important to understand the impact of the GIL on multi-threading in Python, as it limits the parallelism that can be achieved using threads in CPython (the standard implementation of Python).

Inter-thread communication: This involves using techniques such as locks, semaphores, conditions, events, and queues to exchange data and synchronize execution between threads.

Thread-safe code: It is important to write thread-safe code when working with multiple threads, to avoid race conditions and other synchronization problems.