According to textbook publisher Pearson Prentice Hall, the definition of descriptive economics is the branch of economics tasked with gathering data about the economy. Economists present this data as positive facts, which are facts based on sound scientific principles.
Scientists use positive analysis and normative analysis to communicate economic principles. Descriptive economics is comprised of positive analysis because it's fact based and objective. It involves gathering data and presenting it without attempting to communicate what the data means.
Normative analysis looks at factual data, but it results in recommendations that constitute value judgments. Although economists use factual data to form these judgments, the recommendations are subjective because they're based on the economists' opinions of the meaning behind the numbers.