Cascading Style Sheets, commonly referred to as CSS, is a simple design language intended to simplify the process of making web pages presentable. Put simply, CSS handles the look and feel part of a web page or a whole website. With CSS, you can control the color of the text, the style of fonts, the spacing between paragraphs, how columns are sized and laid out, what background images or colors are used, as well as a variery of other effects and styles explained here.
The term cascading in Cascading Style Sheets refers to a specific way in which browsers determine which styles to apply to a specific part of the page. This method is called “the cascade”, and it’s from the cascade that CSS takes its name.