Answer 1

"__init__" is the reserved method in Python classes
it is known as constructor in object oriented concept (OOP)
eg:
class Car(object) :
def __init__(self, model, color) :
self.model = model
self.color = color
Range_Rover = Car("Evoque", "White")
print(Range_Rover.model,Range_Rover.color)

as for init ...
this what I got from Google

In Unix-based computer operating systems, init (short for initialization) is the first process started during booting of the computer system. Init is a daemon process that continues running until the system is shut down

https://en.m.wikipedia.org/wiki/Init