Every time you refer to information that is not your original conclusion and is not common knowledge, you must give credit to where that information comes from. (Whether it's quoted OR paraphrased!)
You will typically note in parentheses the author's/authors' names and relevant page number, if available.
When there's no author, your citation starts with the article title, and your in-text citation will use that.
It's all about making it easy for your reader to make a one-to-one connection by just skimming down the left edge of the Works Cited page.