What is Web Accessibility
The W3C website describes web accessibility as the following:
Web accessibility means that websites, tools, and technologies are designed and developed so that people with disabilities can use them.
Web Accessibility is a legal requirement
Section 508 is a part of the US Rehabilitation Act. This particular part of the law is making sure that IT based solutions and web-based solutions can be used by all including disabled people. Until now Section 508 has been an independent set of guidelines, but a new version is being developed based on WCAG 2.0 level AA and supplemental requirements.
For further reading, please see:
https://webaim.org/articles/laws/usa/
https://support.siteimprove.com/hc/en-gb/articles/206343943-What-is-Section-508-