This is a data extension to GSM and stands for "General Packet Radio Service". This enables devices such as BlackBerry to have always-on access without using up airtime. GPRS simply transmits data over unused airwaves that are not being used for active phone calls. GPRS gives priority to phone calls, so GPRS automatically slows down in busy airwaves to prevent busy signals on other mobile phones. This is why GPRS can give you unlimited 24/7 always-on Internet access, without the need to dial the Internet. It is the most widespread always-on Internet method. BlackBerry uses GPRS for all emails. Speeds are typically between 30 and 70 kilobits per second, depending on conditions and the network. Not all GSM networks have GPRS. All North American GSM networks have GPRS available. GPRS is partway between second generation and third generation, so it is often called a "2.5G" network. GPRS can have fairly high latency, of about 500 milliseconds. For technical information, see Wikipedia GPRS.
Lowercase GPRS on BlackBerry means that you have basic data service but without BlackBerry email support. Also applies to lowercase "1x" for Verizon/Sprint/Bell CDMA and "nxtl" on Nextel iDEN (see below). GPRS BlackBerries will display an indicator "GPRS" when it connects with full data service, and lowercase "gprs" when it is not able to connect to full BlackBerry email/Internet service.