ARIA
ARIA (Accessible Rich Internet Applications) is a set of HTML attributes used to describe the roles, states and properties of complex, JavaScript-driven controls so that assistive technologies such as screen readers can interpret them.
In practice
The most important ARIA rule is that no ARIA is better than bad ARIA – native HTML elements such as button or nav are already accessible and should be preferred over ARIA reconstructions. ARIA is mainly needed where native HTML reaches its limits, for example with tabs, accordions or live regions.