Roaming calls are those made or received when you are physically outside your rate plan's home coverage area. If you are traveling outside that area, you can incur roaming charges when talking to someone regardless of where they are, even if they happen to be standing right next to you. Most roaming charges can be avoided with the selection of a national rate plan (see page 18).
Some people confuse roaming with long distance, leading them to buy a national plan even though they don't use their phone much outside their local area. The above diagram shows the distinction between roaming and long distance for someone who has a local plan. Assuming the plan has free long distance, you will be able to call anywhere in the country from your home calling area using the airtime minutes in your package.
The Evolution of Roaming
The definition of the term “roaming” has evolved over the years. Wireless started as a very fragmented business, with dozens of carriers offering service in limited geographic areas. To enable users to have service outside this limited area, the carriers created roaming agreements, and roaming became known as airtime a subscriber of one carrier used while on another carrier's network. The “outside” carrier would bill the subscriber's carrier for that airtime, and the carrier would pass that charge (with a nice markup) on to their subscriber.
Today, carriers have established networks that cover much of the nation and the above situation occurs much less frequently. However, roaming charges persist as carriers offer low-cost local plans with smaller coverage areas, and then charge roaming outside those areas — usually 69 cents or more per minute. Since much of this roaming is actually on the carrier's own network, these calls are hugely profitable for the carrier.