Primary Literature will be published in scientific journals. The articles will always name the journal, and will frequently have a full citation at the top, as shown here:
Reviews are also in scientific journals. They will often have the phrase "a review" as part of the article title, or before the title in the PDF. The phrase "in this review..." might also appear in the abstract. They too will list the journal name, and often the citation:
Reports (a common type of grey literature) will not have a citation or a journal listed at the top. They will often be written by federal agencies or NGO's. They may have the words "report," "white paper," "working paper" etc. as shown.
