Pieces of Information that Identify the Source Used
A citation is a way to structure pieces of information about the sources whose ideas and words you used when creating your product. These pieces help your audience find these sources for themselves. They also show your audience the quality of your research per your use of different types of sources.
A Way to Attribute Information Written by Someone Else
Citation also plays a crucial role in information ethics. It is important to correctly attribute the words and ideas you use so that you are not stealing someone else's ideas.
Wartburg College covers academic violations in the Honor Code.
Why are there all these different styles?
Blame the Professions
Different professions have decided to create their own rules for citations. These differences tend to emphasize what is important to that profession.
For example, every style puts the author first, and MLA puts the title second and the year last--because the emphasis is on the author, their subject, and differentiating between multiple sources by the same author. When a source is published is not as important to literature and language studies as what the source is addressing.
On the other hand, APA puts the author first and year second--because what matters for these professions, such as psychology, is the currency of coverage of the topic.