In Nursing Science, a primary resource documents original findings. For a journal article, this means that the authors of the article carried out the original research and are reporting their original findings.
In Nursing Science, a secondary resource is writing about the findings of another researcher. For a journal article, this means that the authors of the article did not carry out the original research but are discussing the research of others. This is typically a review or combination of multiple studies in one paper--a literature review, scoping review, or an analysis are common examples of secondary research in Nursing.