question about descriptor

[akbarza]

hi
the below code is in :https://docs.python.org/3/howto/descriptor.html

import logging

logging.basicConfig(level=logging.INFO)

class LoggedAgeAccess:

    def __get__(self, obj, objtype=None):
        value = obj._age
        logging.info('Accessing %r giving %r', 'age', value)
        return value

    def __set__(self, obj, value):
        logging.info('Updating %r to %r', 'age', value)
        obj._age = value

class Person:

    age = LoggedAgeAccess()             # Descriptor instance

    def __init__(self, name, age):
        self.name = name                # Regular instance attribute
        self.age = age                  # Calls __set__()

    def birthday(self):
        self.age += 1                   # Calls both __get__() and __set__()

in the above code, in the last lines is written that calls _set__() and calls both __get__() and ....
why is called __set__ and __get__ ? how does it know to call them? is age in line age = LoggedAgeAccess() the same as age in __init__ method ? please give some explanation.
thanks