What does radio mean in the contact selection instead of mobile or home, and why is it the default?

Question

What does radio mean in the contact selection instead of mobile or home, and why is it the default?
When adding a new contact, the number shows up as "radio" instead of "mobile" or "home" and I have to change it every time. What does "radio" mean and why is it the default? can that be changed?

Answer 1

Radio is a type of phone service offered by certain carriers.  Sprint for instance offers their Sprint Direct Connect Phones (a.k.a Nextel) which have built in Radios.  Short Wave or CB radio type features. Also referred to as Push to Talk services.
http://shop.sprint.com/mysprint/services_solutions/category.jsp?catId=solution_s dc&catName=Sprint%20Direct%20Connect
Think a walkie talkie in your Phone.
I get the Radio option when using Hotmail contacts as the default Contact creator. If I change it to iCloud or Gmail I no longer get the Radio option in the labels.
If you are using a service such as Hotmail/Outlook.com for your contacts the radio option may be present.
You can change which service is the default service to create new contacts with by going to Settings->Mail Contacts & Calendars->Contacts->Default Account
The Radio label is just an identifier for those types of Phones so you know its a number for a radio phone.