What do WCAG and VPAT mean?

WCAG, the Web Content Accessibility Guidelines, is the standard for making a website usable by people with disabilities, including blindness, low vision, color blindness, deafness and cognitive disabilities.

A VPAT, or Voluntary Product Accessibility Template, is the standard form a vendor fills in to report how its product measures against those guidelines. A completed VPAT is called an Accessibility Conformance Report.