Its a way for us to identify the thing you do. To help you prevent having multiple of the same thing running. It comes from the Controller logic. Controllers are all classes in our system that hooks into the life cycle of the host components. Context-API/Observers/... many more... At the end of the day, if your code runs twice then the alias will destroy/stop/clean-out the previous... in the case of observations, you do not want two observations running at the same time, only the latest. In the specific case above the observation is stopped by removing that controller. You can read more here: [Controller](https://docs.umbraco.com/umbraco-cms/customizing/foundation/umbraco-element/controllers#controller-alias) Notice, the observation controller does not need a alias, if not given we will hash the callback and use that as part of the identifier.