There are three types of settings which help control your Budibase app:
General - the name of the app and a description about it, as well as the ability to change the app's URL if you are self hosting.
API keys - When deploying to the Budibase Cloud you need to provide your API keys for the Cloud, this is provided in the app settings.
Danger zone - the ability to perform dangerous actions on your Budibase app, such as delete it if it is no longer required (we recommend exporting beforehand if you desire to do this).
All these settings can be found in your apps settings menu, found by clicking on the cog/gear icon in the builder when you have an app open.