Authoritative, peer-reviewed articles in academic journals have traditionally only been made available to readers upon payment of a fee, whether it's a charge for that one article or a subscription to the journal. Libraries often purchase subscriptions to online services that provide access to a large number of journals for an annual fee.
The Open Access movement (OA) favors making research articles available to all readers, with the intent of supporting further research that is not hindered by the high cost of accessing prior work.
Many university-level researchers argue the benefits of OA, sometimes going to great lengths to make their own work available to the public despite the university's preference for charging a fee to obtain access to that work. Academic journals are able to partly offset the cost of publishing by charging a subscription fee, and often look less favorably on OA initiatives.
Open Access efforts have on occasion led to poor quality publishing. Some lesser known journals that have moved to an OA model have been shown to have lax peer review standards, so readers need to use care when using these materials.