When you visit wireless carrier retail stores or their Web sites or peruse their brochures, you invariably run across this term: The Plan. The Plan is a common term for the contract that describes which services you’re signing up for, specifies how much it costs to use them, and spells out the terms and conditions you must abide by. The two types of plans are described in the following sections.

Prepaid

In a prepaid plan, you pay upfront to use your mobile phone. Increasingly, the prepaid plan is often associated with mobile phones bought from vending machines, drugstores, and similar outlets, but you can buy and use a mobile phone with a prepaid plan almost anywhere, including from most wireless carriers’ retail stores.

The idea is simple: Buy a phone and apply some credit to the account, and then, as you use the phone, the cost for its use is deducted from your credit. After you use up your credit, you can’t use the phone until you “top up” (add credit to) your account. You can pay for more credit over the Internet or at a wireless carrier’s kiosk or retail store — very similar to a prepaid calling card.

If you want more from your phone than just voice services — making and receiving phone calls — don’t choose a prepaid plan. You may find one that lets you send and receive text messages, but prepaid plans rarely let you access the mobile Web or use any other data services (picture messaging or Internet-enabled applications, for example).

Postpaid

A postpaid plan (also known as a contract) is an agreement between you and your wireless carrier that stipulates all rules and regulations regarding your use of the phone and the wireless carrier’s services — and, most importantly, your monthly payment.

Most wireless carriers require you to sign a multiyear contract (two years is standard). Within this contract, you select the services you want on your plan and commit to paying the wireless carrier a specific amount of money each month. In return, the carrier lets you use your mobile phone and the services you selected and agreed to pay for, such as voice, text messaging, mobile Web, games, navigation, e-mail, and more. Any use over the amount specified in the plan is added to your bill at the end of the month, just like your account with an old-fashioned wired phone. If you’re interested in getting access to mobile Internet products and services, this is the type of plan you want.