Which pseudo-class is used to style elements when they are focused?

The pseudo-class used to style elements when they are focused is :focus. This pseudo-class applies styles to an element that has gained focus, typically through user interaction, such as clicking on an input field or navigating to an element using the keyboard. The :focus pseudo-class allows developers to enhance the user experience by changing the appearance of input fields, links, or buttons when they are activated, making it clear which element is currently selected or ready to receive input.

For example, you can specify border color, background color, or other visual styles for an input field when it is focused, helping users to better identify where they can type or interact. This functionality is important for accessibility and usability in web design, ensuring that users can navigate forms and other interactive elements effectively.