A source is generally consider "primary" when it was generated as someone was going about their business. Good examples of primary sources might include letters, diaries, musical score, business records, or photographs. Most often we think of primary sources as something that is unpublished. Digital media have made it possible for larger numbers of researcher and casual users to encounter primary source material.
A source does not necessarily have to be unpublished to be primary source material. An edited diary is still a primary source, as are collected papers. Fiction or poetry is considered primary source material for literary scholars, and a collection of an author's published works would be primary source material to a biographer.
What really determines whether a source is primary or secondary or tertiary is the approach and questions presented by the researcher. This page identifies some primary source collections and items held by the library. The lists you see here are intended only to prod your thinking, NOT list everything we hold
University archives and the manuscript collections consist of unpublished archival material accessible on-site only in Corbitt Special Collections during departmental business hours
Some examples of primary material distributed commercially in various media