In text citations are the brief citations made in the body of your text that point the reader to your full citations on your list of works cited. They can be added at the end of material requiring a citation or incorporated into a sentence.
Example 1: (At the end)
For example, I might include a quotation from a source in my paper. "Skeptical readers may doubt the basis for your work or your conclusions. Others may simply want to double-check them or do more research on the topic. Your citations should point the way" (Lipson 4).
In the above example (Lipson 4) is the in-text citation.
Example 2: (Incorporated into the sentence)
It would also be correct to use the author's name in the sentence. According to Lipson, "Skeptical readers may doubt the basis for your work or your conclusions. Others may simply want to double-check them or do more research on the topic. Your citations should point the way" (4).
In either case your reader should be able to identify the correct citation on your works cited page from the information given in the in-text citation.
The full citation on the works cited page would be:
Lipson, Charles. Cite Right: a Quick Guide to Citation Styles -- MLA, APA, Chicago, the Sciences, Professions, and More. 2nd ed., U of Chicago P, 2011.
Additional examples can be found in the MLA sample papers.