How does "def" work in python?

Question

Well I have seen "def" in lots of programs but I never understood the function. I am a newbie in python so I need a basic explanation about "def".And I would be really happy if you can add a basic explanation too. Thank you for your attention :)

Answer 1

Python
>>>help("def")

Answer 2

"def" is used to declare a function..Like :-
def functionname():
#function content here

Without it you cannot start a function.
It is then followed by the function name and parentheses