[Tutor] diferent between " "(empty string) and None as condition

[Emin Kovac]

pasword = ""
while not pasword:
pasword = input ('Pasword: ')

username = None
while not username:
username = input('Username: ')
My question is when should I or what is better to use as
condition empty string (" ") or None?
Anyway, what is different between an empty string and None