Accessibility(a11y) in Web development means that websites, tools, and technologies are designed and developed so that people with disabilities can use them. A11y is the right thing to do. Providing accessible sites is part of the law in some countries.
Web Content Accessibility Guidelines(WCAG) is the primary specification adopted around the world and describes how web content should be created so it will be accessible to people with disabilities. It’s a large and detailed document. The WCAG 2.1 at a Glance provides a paraphrased summary of WCAG 2.1.