What is special in /Applications/ folder? What happens when an .app bundle going copy to the /Applications/ folder? Are there any processes starting, any preferences copied to /Library/ ? Is a copy to /Applications/ folder a special trigger/event for the OS X?

I found that if I just copy Xcode then com.apple.dt.Xcode.plist appears in user's Preferences folder.
With the exception of installing app with package manager, there is no special events if you only copy application to any folders. The preferences stored in Library or Application Support are created when you run the application for the first time.