When searching various Library and online sources, the button, when present, can be used to locate an item in the Library Catalog, to gain access to the full-text of an article, or to send interlibrary loan orders for items that the Library does not own.
Almost all Library databases can be accessed from off-campus. The easiest way to do this is to use links from the main Library website or this and other Subject Guides. You will then be prompted for your CNetID and password to authenticate yourself as an authorized user.
If you find sources through Google Scholar or other search engines, you may not automatically get access to Library resources. IT Services has created the ProxyIt bookmarklet for these situations.