What is app.config for?

Question

Settings.settings generates Settings.Designer.cs which presumably generates app.config which then is copied to output directory as

Answer 1

If you don't have the config file, it uses the default values from the designer. However, the config file allows users/administrators to easily change settings - such as the server you talk to, themes, etc. If you don't have the file, where would you expect those settings to be stored?

You can have per-user settings as well as per-application settings, which are stored in different locations.