The WCAG guidelines were updated from version 2.0 to 2.1 in June 2018. The updates in 2.1 cover changes in technology that have occurred since the previous version, and also address areas that were underrepresented in 2.0. What does this mean for you? Not a lot right now. The compliance level targeted is still WCAG 2.0 Level AA, and the 2.1 success criteria are in addition to those already existing in 2.0.
The ADA is the Americans with Disabilities Act, passed almost 30 years ago in 1990. This act was originally put in motion pertaining solely to physical location. It requires establishments to provide people with disabilities easy access to various levels throughout the business. This act was set to achieve an equal experience to all people, handicapped or not.