CSS selectors are used in HTML to style and format the content and layout of a webpage. HTML is used to create the structure of a webpage, defining the various elements and their content. CSS is used to define the presentation of those elements, such as their color, size, position, and other visual properties.
By using CSS selectors, developers can target specific HTML elements and apply styles to them. For example, they can select all h1 headings and apply a specific font and color to them, or they can select all p elements within a particular div and change their background color.
CSS selectors also allow developers to apply styles based on specific conditions, such as the element's class, ID, or other attributes. This allows for more precise targeting of specific elements and more flexible styling options.
In summary, CSS selectors are used in HTML to control the visual presentation of web content, allowing developers to create a more visually appealing and engaging user experience.