You may be hearing and reading a lot about the terms “primary and secondary research.” Actually, they are fancy terms to describe very simple concepts. This video does a nice job of explaining the concepts.
If you heard it from someone else, as “second-hand” information, it’s secondary research.
If you were the first person (the primary person) to discover something, then it’s primary research.
Secondary research is important because it allows you to catch up on what everyone else has already found and researched (hopefully thoroughly). After a literature review or other form of secondary research, you will be prepared to venture into the topic with confidence because you will know the existing knowledge on the topic.
Primary research is special because you are the first (or one of the few) people to study the phenomena. Considering design is always changing and the ways people react to it are seldom the same (depending on culture, time period, context, and many other factors), it’s very likely your research may be exploring uncharted territory.