A context manager is a Python object that defines a runtime context to be used with the with statement. It is used to set up and tear down resources that need to be acquired and released in a predictable way, such as opening and closing a file, acquiring and releasing a lock, or connecting and disconnecting from a database.

        The with statement is used to wrap the execution of a block of code with methods defined by the context manager. When the with block is entered, the context manager's __enter__() method is called, which sets up the resources needed for the block of code. When the block of code is exited, the __exit__() method is called to clean up the resources.

        Context managers can be created using the contextlib module, or by defining a class that implements the __enter__() and __exit__() methods. Context managers can also be used as decorators using the @contextmanager decorator from the contextlib module.