Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation
semantics (the look and formatting) of a document written in a markup language such as
HTML or XML.
Major browsers implement CSS parsing engines for formatting or styling the pages using CSS
syntax. CSS was introduced to keep the presentation information separate from the markup
or content.
In CSS, pattern-matching rules determine which style should be applied to elements in
the DOM. These patterns, called selectors, may range from simple element names to rich
contextual patterns. If all conditions in the pattern are true for a certain element, the selector
matches the element and the browser applies the defined style in CSS syntax.
Selenium WebDriver uses the same principles of CSS selectors to locate elements in DOM. This is
a much faster and more reliable way to locate the elements when compared with XPaths.