CSS selectors are a powerful way to identify objects in WebDriver, allowing for more flexible and readable bindings that can be easier to maintain than XPATH locators. CSS selectors use a combination of element selector and value to identify web elements within a web page. Simple ID selectors use the "#" symbol, while direct child selectors use the ">" symbol. Child or sub-child selectors are denoted by whitespace. Classes are identified using the "." symbol. Advanced selectors include next sibling, attribute values, and pseudo-classes such as nth-child, which can be used to select specific elements within lists. Partial string matches can also be achieved using ^=, $=, and *= operators. While some pseudo-classes are deprecated or not supported by all browsers, many are implemented in the current CSS Selectors level 3 standard and can be used with Selenium for more efficient testing.