There are several reasons why it is important to cite your sources properly.
Popular Sources
Peer Reviewed (sometimes called Scholarly or Academic
Scholarly Sources
There are guidelines of what to include and in what order for every citation style. Here are the basics for the two most common sources.
For an article:
For a book:
A subject heading or a descriptor is a tag used to describe the article. These tags come from a list and reflect the terminology discipline of the database. (e.g. In medicine you search myocardial infarction not heart attack.)
What are the benefits?
How do you figure out which terms are a subject heading?
What if you don't find one?