PsycARTICLES looks like many of the other article databases available through the library. How it differs is in its selection of content. The articles in this database are published by the American Psychological Association and related publishers. So when you search it, you are limiting yourself to fairly prestigious journals. The articles you turn up are more likely to be high-status than articles you turn up from more general databases.
When you're on the results pages, PsycARTICLES allows you to exclude book reviews and other non-article content from your searches.
On the Advanced Search screen, you'll find many more limiters allowing you to limit by age group, type of population studied (e.g. Human or Animal), methodology and so on.
The thesaurus classifies the articles in PsycARTICLES by subject and allows you to limit your results to only articles specifically about certain concepts.
Click the Cited References link to get a list of the works cited in the article. You will also see the number of times the article has been cited in PsycARTICLES; if the number is high, this is a sign that the article is influential. (You can also look up the article in Google Scholar to get a sense of how influential it has been.)
If the article is available in full text in PsycARTICLES, you'll be able to click through to it. Even if it isn't, you should be able to find an abstract if you search for it in PubMed, and you may even find full text by searching for it in OneSearch or Google Scholar.