what does def in python mean code example

Example 1: how to use def in python

def functionName(variable):
  //function content

Example 2: explain def in python

def greet(name):
    """
    This function greets to
    the person passed in as
    a parameter
    """
    print("Hello, " + name + ". Good morning!")

Example 3: what does * mean in python in functions

>>> numbers = [2, 1, 3, 4, 7]
>>> more_numbers = [*numbers, 11, 18]
>>> print(*more_numbers, sep=', ')
2, 1, 3, 4, 7, 11, 18