A schema is a way the mind helps organize and interpret information about the world, self and others. 'Labelling of self and others' is a form of assigning an idea to something or someone (including self.)
In regards to self, this is the act of choosing an action or behaviour that we are doing or have done in the past, and deciding that is who we are. For example, if a person displays anger once or several times, they may believe they are an 'angry' person. Someone who does not pass an exam or does not achieve a specific business goal, may label themselves as a 'failure.' This can develop a sense of helplessness, to the behaviour shown, and is often a massive over-generalisation. Labelling can also apply to others, for example because one ex-partner cheated on you, you believe that ‘all men or women are bad.'
It's important to recognise that the behaviour is not the person and to see the behaviour as separate from them or a part of them.