## TL;DR

ARIA provides attributes that enhance HTML accessibility for assistive technologies (screen readers). It defines roles (`role='button'`), states (`aria-expanded`), and properties (`aria-label`). The first rule of ARIA: don't use ARIA if native HTML already provides the semantics.

## Core Explanation

Key patterns: `aria-label` for accessible names, `aria-labelledby` to reference another element, `aria-describedby` for descriptions, `aria-live` for dynamic content announcements (polite/assertive). `role='alert'` for important notifications. ARIA does NOT change behavior — `role='button'` doesn't add click handling or keyboard interaction.

## Further Reading

- [WAI-ARIA 1.2 (W3C Recommendation)](https://www.w3.org/TR/wai-aria/)