A deployment slot is a live, runnable copy of your application in Azure App Service that runs alongside your production environment.
Let’s see it in action. Imagine we have a web app, my-awesome-app.azurewebsites.net, currently serving live traffic. We want to deploy a new version.
First, we create a new deployment slot. In the Azure portal, navigate to your App Service, then under "Deployment," click "Deployment slots." Click "Add Slot." We’ll name this slot staging.