The :where() CSS pseudo-class function takes a selector list as its argument, and selects any element that can be selected by one of the selectors in that list.| MDN Web Docs
The :is() CSS pseudo-class function takes a selector list as its argument, and selects any element that can be selected by one of the selectors in that list. This is useful for writing large selectors in a more compact form.| MDN Web Docs
The CSS nesting module allows you to write your stylesheets so that they are easier to read, more modular, and more maintainable. As you are not constantly repeating selectors, the file size can also be reduced.| MDN Web Docs
The :not() CSS pseudo-class represents elements that do not match a list of selectors. Since it prevents specific items from being selected, it is known as the negation pseudo-class.| MDN Web Docs
The functional :has() CSS pseudo-class represents an element if any of the relative selectors that are passed as an argument match at least one element when anchored against this element. This pseudo-class presents a way of selecting a parent element or a previous sibling element with respect to a reference element by taking a relative selector list as an argument.| MDN Web Docs