Lumen is a new project from Laravel creator Taylor Otwell. It's a "micro-framework", meaning it's a smaller, faster, leaner version of a full web application framework. PHP has two other popular micro-frameworks, Slim and Silex.

laravel lumen api

Lumen has the same foundation as Laravel and many of the same components. But Lumen is built for microservices, not so much for user-facing applications although it can be used for anything.