HTML stands for HyperText Markup Language. It is the standard markup language used to create and structure content on the web. Elements like headings, paragraphs, links, and images are defined with tags in HTML.
CSS (Cascading Style Sheets) controls the presentation of HTML content. It can adjust colors, spacing, typography, and layout behavior. By applying selectors, you can target elements and define styles that respond to different screen sizes or states.
Using the native details/summary elements provides built-in accessibility. The keyboard focus and screen reader support help ensure that the widget is usable by a wider audience without extra scripting.