A docstring is a string - always using triple quotes - that's placed at the top of files, classes and functions. A docstring should contain a clear explanation of what it's describing. You can also include descriptions of the subject's parameter(s) and what it returns, as shown below:

def greet(name: str, age: int) -> str:
    Return a string that greets the given person, using their name and age.

    :param name: The name of the person to greet.
    :param age: The age of the person to greet.

    :return: The greeting.
    return f"Hello {name}, you are {age} years old!"
You can get the docstring by using the inspect.getdoc function, from the built-in inspect module, or by accessing the .__doc__ attribute. inspect.getdoc is often preferred, as it clears indents from the docstring.

For the last example, you can print it by doing this: print(inspect.getdoc(greet)).

For more details about what a docstring is and its usage, check out this guide by Real Python, or the official docstring specification.