The CSS means Cascading Style Sheets. It indicates that the HTML elements displayed on screen, paper, or in other type of media. It saves a lot of work. By using Cascading Style Sheets programmer can control the layout of many web pages all at once. These CSS are stored in the file of .css extensions file.
Cascading Style Sheet is opted to define styles of the web pages. It also defines the web page design, layout and variations in display for different types of the devices and their screen size. This way CSS solved a big problem. However, HTML is not more focused on formatting a web page and it does not contain more formatting tags.