Skim each of the articles linked below. (Log in with g# and password if prompted)
read the first paragraph or two
scroll through the article and notice its format and writing style
review information provided at the end of the article
scan the rest of the page where the article lives for additional clues as to which type of article it is
Use these examples to familiarize yourself with the differences between background information articles, scientific news articles, primary literature articles and review articles.