What does this technical specification about GSM iPhone mean?
If you keep reading...
Connectivity

In contrast to Steve Jobs' announcement at WWDC 2010, recent Federal
Communications Commission documentation has shown that the iPhone 4
contains a penta-band 3G UMTS antenna, not a quad-band 3G UMTS radio,
as advertised by Apple.
According to the FCC documentation filed by
Apple, the radio inside the iPhone 4 supports 800, 850, 900, 1,900,
and 2,100 MHz. The 800 MHz frequency, which is most commonly used in
Japanese mobile phones, is not advertised as being supported by
Apple.[51] However, the 800 MHz band is a subset of the 850 MHz band,
which probably explains why the device is advertised as
quad-band.[citation needed] The chip-sets were manufactured by
Skyworks Solutions[52] and Infineon for GSM version.