What is the purpose of 'self' in Python?

self is a reference to the current instance of the class, used to access instance attributes and methods. It must be the first parameter of instance methods (though not passed when calling). self.attribute creates/accesses instance variables; without self, it's a local variable. Unlike Java/C++ where 'this' is implicit, Python requires explicit self. Convention is to use 'self' though any name works. Class methods use 'cls' instead of 'self'. self enables each object to maintain its own state.