OneSearch is considered a "discovery tool". This means that it searches "similar" to Google, but only searches out resources the library has specifically subscribed to (at this point). OneSearch looks for books, ebooks, videos, articles from library databases and then pulls in the results. You get a broader search even when limiting just to journal articles.
When using a specific library database you will often have more specific limiting features to fine tune your search for articles that OneSearch does not provide.
Address: