A primary source is an original object or document created at the time the historical events occurred. It is the raw material or first-hand information. In the natural and social sciences, the results of an experiment or study are typically found in scholarly articles or papers delivered at conferences, so those articles and papers that present the original results are considered primary sources.
Examples of primary sources:
A secondary source is something written about a primary source. Secondary sources include comments on, interpretations of, or discussions about the original material. You can think of secondary sources as second-hand information. If I tell you something, I am the primary source. If you tell someone else what I told you, you are the secondary source.
Examples of secondary sources:
A tertiary source can be a compilation of primary and secondary sources or a work that uses secondary sources for its research. Sometimes it is difficult to tell the difference between secondary and tertiary sources. Some source types can be either secondary or tertiary, depending on the individual source (textbooks, for example, can be secondary or tertiary sources). For introductory-level coursework, it is frequently acceptable to use tertiary sources, but instructors in higher-level courses will probably ask you to avoid them.
Examples of tertiary sources: