iPhone provisioning

Question

I have an iPhone that is provisioned for distribution (ad hoc) only, for testing. It is not included in a development provision, but is included in an ad-hoc provision.

Why is it I can plug this iPhone into Xcode and run my app on it from Xcode? The Xcode scheme has "Run" set to "Debug." Doesn't this require a developer provision?

If not, then what is the difference between a development device provision and an ad-hoc provision?