In order to understand what semantic actually means you'll have to know the word "semantically". This word means to use in a way that properly aligned with meaningful words. Many HTML have meaning tags for semantic. This element use opening and closing tags, itself carry information about different type of contents. In the code, you'll see h1 as a heading and it tags the mean of the content h1 element that constitude the very most important heading. Writing semantic markup is based on creating web content that both humans and computer could understand
Section-508 and Accessibility
Section 508 is an Rehabilitation Act, that amended by the Workfore Investment Act of 1998. Section 508 requires the federal agencies to make Information and Communication Technoloy (ICT) such as technology, train on-line and websites accessible for everyone. In other words, federal employees with disabilities are able to work on the accessible computers, phones, and equipement in their offices. Taking on-lin training or any access to the agency's internal website to locate any needed information. This mean that if someone has disability applying for a job the federal goverment or a person who uses an agency's website to get information about a program of any such, have to complete a form online to accessible information and resources. ICT are equipement or system that uses to create, convert, duplicate or access information and data.
How they are all related
Semantic Markup and Section 508 is related because both create websites. Also, they both have improved technology for humans. When you write a semantic markup mandatory it will be more accessible styling that will make up bad markups.