Laravel Valet is a lightweight development environment for macOS that allows developers to host and run PHP applications locally in their local development environment, using a custom URL. This eliminates the need to manage host files and makes it possible to launch applications without requiring MAMP or Vagrant. Valet uses ngrok to make local applications publicly accessible on the internet, enabling collaboration and simplifying reviews before pushing to production. The tool provides various features such as secure links, domain generation, and support for PHP, making it a useful tool for developers.