WCAG 2.0 / WCAG 2.1 represent the latest versions of the Web Content Accessibility Guidelines. These are the standards that the majority of national and sub-national (provincial, state, etc) legislation is based on, including ADA in the United States, and AODA in Ontario Canada.
WCAG standards include guidelines for content, code, and technical guidelines for how colour, interactivity, and more is handled on a website.
All organizations should be striving for a WCAG 2.0 AA rating for their website in order to meet general accessibility guidelines. A, AA, and AAA ratings define the measure of adherence to the standards presented by the WCAG guidelines.