A Dingtone phone number is a real phone number just like any other regular number with a country code and clear numbers, which is different from other calling apps that provide random number strings or alphabets.
By default, as the first call is made on Dingtone, a US number will be given to its users for a couple of months before it gets expired. If they expect it to be unlimitedly used, they can purchase it.
Currently Dingtone has phone numbers belonging to many countries, including U.S., Canada, England, Belgium, Spain, Russia, Finland, and Sweden. More countries will be gradually added soon.
These phone numbers are exactly the same as phone numbers assigned by Verizon, AT&T, and Sprint and can be used to call and text to anyone, even those not using Dingtone.