Primary research refers to the kind of research where researchers form a hypothesis, observe the results, and publish their findings. Primary research includes data that is being reported for the very first time and must be considered within its context.
Primary research is particularly useful when one is compiling lots of information in order to make generalizations and recommendations in the form of systematic reviews (see secondary research below).
Secondary research is when a researcher collects and reviews lots of primary research in order to make generalizations and recommendations. Secondary research often takes the form of literature reviews, systematic reviews, and meta-analyses.
Secondary research is perfect for people who are looking for evidence-based practices to inform their decision making.