What is the purpose of the Rehabilitation Act Section 508 and its relationship to Technology Enhanced Learning Environments? https://www.hhs.gov/web/section-508/index.html

The purpose of Section 508 of the Rehabilitation Act of 1973 is to ensure that all web content is accessible to people with disabilities; by ensuring access, Act 508 ensures that learning environments where information and communications technology are used are also accessible to people with disabilities.
According to the U.S. Department of Health and Human Services, "Section 508 requires that all website content be accessible to people with disabilities. This applies to Web applications, Web pages and all attached files on the intranet, as well as, internet." This only applies to federal websites, however—it does not regulate the entire internet. 
Technology-enhanced learning environments refer to learning environments that make use of information and communications technology. This can include computers, tablets, the internet, and many other things. Learning environments support the use of active learning, in which students engage in active rather than passive modes of learning. Section 508 ensures that students with disabilities in technology-enhanced learning environments can access federal sites. This helps keep them from being excluded in any active learning processes that involve federal websites or content.
Section 508 was first enacted in 1998.
https://link.springer.com/chapter/10.1007%2F978-1-4020-6670-2_11

https://www.hhs.gov/web/section-508/index.html