CSS stands for Cascading Style Sheets, and it is used to control the styling and layout of web pages. With CSS, you can style HTML elements in various ways, such as changing colors, fonts, sizes, and positioning.

The term "Cascading" refers to how styles are applied at different levels (e.g., inline, internal, or external styles), and if multiple styles apply to the same element, the "cascading" rules determine which style will take precedence.