BEM is a naming convention that makes front-end code easier to understand and maintain. It stands for Block, Element, Modifier. A Block is a standalone component, an Element is a dependent part of a Block, and a Modifier changes the appearance or behavior of a Block or Element. BEM has simple rules for naming classes with prefixes and separators to identify each part. Applying BEM helps code be modular, flexible, and support partial loading. It also works well with component-based frameworks like React and Vue. Real-life examples from Blibli Travel and a sample framework demonstrate how to implement BEM.