There are two components to any source of information you use: the ideas and the words.
There are two ways of using information in your work: direct quotes and paraphrasing. (We'll call summarization a kind of large-scale paraphrase. The big idea of a book or article may be summarized, while a sentence or two at a time may be paraphrased. Same principle applies to both, however.)
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. You will typically note in parentheses the author's/authors' names and relevant page number. This allows you to give credit without wasting excessive page space or disrupting the flow of the paper.
If an article doesn't have an author, your Works Cited citation will start with the article title, and your in-text citation will reflect 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.