Netlify is highlighting a different feature each day in December, encouraging users to deploy their registered domains. Netlify Dev is a tool that brings utilities to the local development environment, replicating edge logic and routing rules for testing and development. It can be installed globally with npm install -g netlify-cli and provides features such as automatic site detection and serving, environment variable availability, and serverless function compilation. Netlify Dev aims to unlock creative potential by making these tools accessible in a local development environment.