Core answer
Start here. This is the direct spoken answer to practice first.
Why this question matters
Flags make deployment less dramatic when used well, but they also add configuration and lifecycle risk. This drill matters because the production behavior is shaped by platform configuration, code boundaries, and the operational path the team will use during a real incident.
Feature flags let me deploy code separately from releasing behavior. I can ship a feature disabled, swap the new App Service slot, verify the app is healthy, then enable the feature for a small audience or environment. If the feature causes errors, I can turn it off faster than building and deploying a new artifact.