In iOS, most of your apps have their settings tucked away in the main Settings app -- not very useful if you're in the app itself and want to tweak something. In iOS 7, you can ask Siri to jump right to that app's settings for you.
For example, say you're in the Mail app and you want to change some of the Mail-specific settings. Instead of going back to your home screen, opening the Settings app, and heading to "Mail, Contacts, Calendars," you can just open Siri and say "launch settings." She'll take you straight to the settings for the app you're in -- in this case, Mail. This works with third-party apps as well.