CSSWizardy say it better than me: "BEM – meaning block, element, modifier – is a front-end naming methodology thought up by the guys at Yandex. It is a smart wa

CSSWizardy say it better than me: "BEM – meaning block, element, modifier – is a front-end naming methodology thought up by the guys at Yandex. It is a smart way of naming your CSS classes to give them more transparency and meaning to other developers. They are far more strict and informative, which makes the BEM naming convention ideal for teams of developers on larger projects that might last a while." http://csswizardry.com/2013/01/mindbemding-getting-your-head-round-bem-syntax/ http://csswizardry.com/2013/01/mindbemding-getting-your-head... But basically: agreed rules for how to name and format css to make it maintainable and performant in big projects.