Why is the "spam" variable recognized as the self contend and the "hello" variable as the other content?

Question

My Question is, how does it identify which variable ("spam" and "hello" in this example) is the self and which the other content? Where does it say which is which?
And why are not both identified as self, since both are in the Special String class.

This is the code from the python course, Module "Object-Orienting Programming", Section 3/8 "Magic Methods & Operator Overloading.

class SpecialString:
def __init__(self, cont):
self.cont = cont

def __truediv__(self, other):
line = "=" * len(other.cont)
return "\n".join([self.cont, line, other.cont])

spam = SpecialString("spam")
hello = SpecialString("Hello world!")
print(spam / hello)

Thanks for answers :)

Answer 1

The First one is the self and the secon the other.
self / other