[Pharo-users] Please explain self

I understand if you have Class A with methods p and q that you can call q from p doing: self q But there are some cases where a method doesn’t exist but self is still used. I found a tutorial on creating a Reddit type app and it had a .mcz which I loaded. Here is an example from Class StLoggedInComponent and method refreshReport: self report rows: (self session user tasks select: self filterBlock). There is a method ‘report’ so I understand that, but there is no method named ‘session’ so what is the use of self? And Class StDatabase has method ‘updateTask:’ has: self subclassResponsibility. But no method called ‘subclassResponsibility’ exists in the Class. Also, Class StLoggedInComponents has method ‘testTasks’ with this: ^ self class testTasks What is ‘self class’? Thank you.