Netlify is highlighting a different feature each day in December, including serverless functions called `Background Functions`. These functions can run long-running tasks without interrupting the main execution of a site. They are version-controlled and built along with other site components. Background Functions allow developers to write functions in JavaScript, Typescript, or Go and deploy them as part of their Netlify site. The functions can be used for tasks that require more time than what is available for serverless functions, such as data processing or API calls. When a background function is successfully executed, the result is typically passed to another destination rather than the originating client. Background Functions are currently in beta but offer an alternative solution for developers who need to handle long-running tasks.