Are WAI ARIA attributes required for WCAG 2.0 level AA compliance?

As explained in my answer on User Experience SE, WCAG 2.0 doesn't require the use of WAI-ARIA.

1. Is WAI-ARIA part of WCAG?
2. Is WAI-ARIA required?
3. What is WCAG 2.0 level AA compliance?
4. What is WAI-ARIA used for?

Is WAI-ARIA part of WCAG?

WAI-ARIA can be used to help developers create widgets, applications, and web interactivity in general that meet WCAG recommendations.

Is WAI-ARIA required?

The WAI-ARIA aria-required property indicates that user input is required before submission. The aria-required property can have values of "true" or "false". For example, if a user must fill in an address field, then aria-required is set to "true".

What is WCAG 2.0 level AA compliance?

WCAG 2.0 Level AA: Acceptable compliance

This conformance level is used in most accessibility rules and regulations around the world, including the ADA. To meet WCAG 2.0 Level AA conformance, the website is usable and understandable for the majority of people with or without disabilities.

What is WAI-ARIA used for?

WAI-ARIA, the Accessible Rich Internet Applications Suite, defines a way to make Web content and Web applications more accessible to people with disabilities. It especially helps with dynamic content and advanced user interface controls developed with HTML, JavaScript, and related technologies.