Azure deployment with VSTS CI and deployment slots

Understanding Deployment Slots in Azure App Services azure deployment slot A custom warm-up is a URL that Azure will hit after code is deployed to the offline deployment slot or slots This gives the app a chance to run azure app service slot Azure Web App deployment slots are separate instances of your application that allow you to deploy and test changes before making them live

azure deployment slot setting Azure Function deployment slots are offer seamless delivery and already in GA But how they work and why they are different from non-serverless plans?