WCAG, short for the Web Content Accessibility Guidelines, is the international standard for making a website usable by people with disabilities. That includes someone navigating by keyboard because they can't use a mouse, a blind visitor listening through a screen reader, and a person with low vision who needs strong colour contrast. The guidelines come in three levels. A is the floor, AA is the level most laws and government contracts ask for, and AAA is the strictest. So when you hear "WCAG 2.2 AA," that is the version of the guidelines and the level your site is being measured against, and AA is the bar a Canadian public-sector site is expected to meet. None of this is vague good intentions. WCAG is a set of specific, testable rules. Images need text descriptions, video needs captions, and when you tab through a page the outline showing where you are has to be visible. I treat AA as the starting point on every build rather than something to add later, because building it in costs far less than retrofitting it, and the work that helps a screen-reader user usually makes the site clearer for everyone.
Glossary entry