Positive economics involves statements based on facts or evidence, free from subjectivity. They can be tested scientifically and proven.
Normative economics involves statements about what should be done based on societal norms, and therefore they're based on subjective evaluation. They can't be proved or disproved scientifically.
'Ceteris paribus' is a latin expression meaning 'other things equal'. This means that all other things are assumed to be constant or unchanging.
