A citation is a way to give credit for ideas that are not your own when you do research and also a way to validate your ideas by pointing to supportive research and writing. The basic pieces of information included in any citation are the author, publisher, date of publication, place of publication, name of publication, database information, and often the date the item was accessed. The order the information is listed is called "style." Using the wrong style does not mean you've plagiarized, but you should use the same style throughout your document and may be required to use a particular style. At Garnet Valley, we use a standard style format called MLA, or Modern Language Association, format.
Sometimes you get those complicated issues, like a quoted source within your quoted source. Here is an explanation of how to handle that in Turabian Style, which is very similar to MLA.