What's different between ground setting and ring set in the Enigma machine? I am writing a python program for the Enigma machine. I know what the ground setting (Grundstellung) is but I don't know the difference between ground setting and ring setting. 


What's different between ground setting and ring set in the Enigma machine?
Terms
As stated on Wikipedia:

Ring settings (Ringstellung) – the position of each alphabet ring relative to its rotor wiring.
Starting position of the rotors (Grundstellung) – chosen by the operator, should be different for each message.


Functions
The ring setting changes the output letter of a rotor. A rotor has a fixed permutation installed (by the wiring) as seen here, i.e. one rotor would encrypt the letter A to the letter G. After one encryption the rotor would turn and the next wiring comes into effect and the new encryption of the letter A would now be encrypted to the letter C.
With the ring setting you could additionally change this fixed permutation of the rotor, i.e. with a ring setting of B (a.k.a. 02) it would change the output of the rotor. It functions like a caesar cipher. Using the example above with the ring setting of B would change the letter A to the letter H (because B is mapped to A (difference of 1) H is mapped to G).