Primary sources are first-hand observations or experiences of an event. They can also be the original sources of information before they have been analyzed, such as statistical data sets and original creations, such as works of art.
Secondary sources are created after an event occurred and offer a review or an analysis of the event; they provide an interpretation of the primary source.
When searching the library databases or open web for information resources, you will need to evaluate whether the sources you find are primary or secondary. They are usually not labeled as one or the other, so you will need to make that determination. Your librarian can help.