SMACSS stands for Scalable and Modular Architecture for CSS. It is a style guide that helps developers create maintainable and scalable CSS code. By organizing styles into categories, SMACSS promotes a consistent approach to styling web applications, making it easier to manage and update. The framework divides CSS into five categories: Base, Layout, Module, State, and Theme. Each category serves a specific purpose, allowing developers to structure their styles logically. This modular approach enhances collaboration among team members and improves the overall efficiency of the development process.