The only purpose of comments is to make yourself or others a note, did I understand it correctly?

Answer 1

Exactly. It exists solely to help others read your code and make reminders for yourself and co-workers.
Might as well prove useful for debugging ("deleting" a line of code temporarly).

Answer 2

Yes, but comment scripts exist too:

// cout << "this is a commented script"
/*
cout << "this is a multiline commented script"
*/