A few people has asked me for a BlackBerry device primer. Here it is. Not exhaustive but will help if you choose if you're buying one of these devices. Unlike Apple, there are subtle variations among seemingly identical BlackBerrys depending upon the country and carrier. More details at the BlackBerry site.
Basically, there are four form factors. All of them have the same software functionality--though some are now shipping with the 5.0 operating system rather than 4.x, depending upon carriers. The first two form factors are aimed more at consumers, the second two more at corporate, though those lines are blurry.
Pearl. This is the smallest BlackBerry. In both flip-phone (two almost identical variants) and bar-phone (four variants) it features the smallest screen and a SureType keyboard that has two letters per key. The keyboard works surprisingly well, once you learn to trust it. Some versions have Wifi. Some have GPS. All current ones have cameras.
Curve. This is the second smallest. It's often the cheapest and doesn't seem to be as well made as other full-keyboard BlackBerrys. Keyboard has smaller keys with gaps between them. Newest model has a trackpad instead of a trackball. GPS. Wifi. No 3G. Three variants currently listed on the BlackBerry site.
Bold and Tour. The original Bold was the largest of the current BlackBerrys. This has been replaced by one that is very similar to the Tour but not identical. Bold is GPS (in the U.S. that means AT&T and T-Mobile); Tour is CDMA (in the U.S. that means Verizon and Sprint). Tour2 (which might be renamed as a Bold for CDMA) will close the gap between the two by switching to a trackpad and including WiFi. All are 3G. These devices are the corporate workhorses of the BlackBerry line and are very well made.
Storm. This is a CDMA model and is the only BlackBerry without a physical keyboard. The Storm2 improved the SurePress "clickable" touchscreen and features surprisingly good typing feel. This is the only BlackBerry with a screen the size of an iPhone or Android phone. WiFi and 3G. Like the Bold and Tour, high quality manufacturing is evident.