Pretty much everything you can do in HTML is accessible by default because Microsoft, Apple, and Google built Edge, Safari, and Chrome to adhere (more or less) to WCAG specifications.
Let’s take tabs as an example. In the beginning if you wanted to have a page with 3 tabs on it, each of which had different content you actually built the page 3 times, ensured the header was identical, and used links to move between the tabs. A screen reader user was fine because each time they clicked a tab (link) it took them to the top of a page and they got all the content.
Enter ARIA, which allows people building custom components like tabsets to declare that a thing has a role of tab panel or a role of tab, so that the screen reader knows. It can even provide values and accessible names to things that would otherwise go with out.
Learning ARIA is complex 1, but unless you or your organization will only ever use HTML out of the box, there’s a good chance you’re going to need it.
- Accessibility Fundamentals – Disabilities, Guidelines, and Laws at Deque University