How to write meaningful docstrings?

What, in Your opinion is a meaningful docstring? What do You expect to be described there?

For example, consider this Python class's __init__:

def __init__(self, name, value, displayName=None, matchingRule="strict"):
    """
    name - field name
    value - field value
    displayName - nice display name, if empty will be set to field name
    matchingRule - I have no idea what this does, set to strict by default
    """

Do you find this meaningful? Post Your good/bad examples for all to know (and a general answer so it can be accepted).