ARIA is an acronym for Accessible Rich Internet Applications. It is a set of special attributes and tags standardized by the World Wide Web Consortium (W3C) to make more complex internet applications accessible to assistive technologies like screen readers and voice control.
Instead of focusing on webpages, the intent of ARIA is to make complicated web apps accessible that do not necessarily conform to the page model. These apps often endeavor to look as much as possible like desktop apps rather than webpages, dynamically load content using AJAX rather than refreshing the entire page, and contain more complicated controls like menu bars, multi-select grids, sliders, and tree views. Google Docs and Google Mail (Gmail) are good examples of this type of more complex web app.
In order to make these apps accessible, ARIA allows developers to use HTML attributes to explain to assistive technologies exactly what type of control they’re building and how it works.
For example, if a developer uses ARIA to identify something on the webpage as a checkbox, screen readers will identify it that way, even if it’s not part of a form and not using the standard checkbox control. However, ARIA only controls how screen readers and other assistive technologies recognize controls on the webpage. The developer is responsible for making sure that the controls behave correctly by handling keyboard and mouse input (for instance, on Windows, the “space” and “enter” keys should check and uncheck the box, and so-on) according to the interaction standards of the users operating system (for example, these are the standards for Windows developed by Microsoft). This means that while correctly-used ARIA tags can make a web app completely accessible, incorrectly used ARIA tags can decrease accessibility and introduce buriers and confusion to assistive technology users.