If you login to your account in Voxofon application on your Android device, navigate to "Contacts" section you will see two tabs: Voxofon and Phone contacts.
Voxofon contacts are the ones that you have created via Voxofon application. They will also be synced in Web application as well as on other platform devices if you login with your account e.g. on iOS device. You can delete and edit these contacts directly from Voxofon application.
Phone contacts are the contacts from your Contacts Book on your device. They can be deleted or edited from your Phone Contacts and cannot be deleted/edited via Voxofon application.