DIfferent parts of the world use different satellites to transmit the cell phone calls. The 4 bands are 850 / 900 / 1800 / 1900. America generally uses 850 and 1900 bands, while the other two bands are used by the rest of the world. I think Europe uses 900 band So if you plan to travel to Europe, you'd technically only need a tri band phone. Might save you some money. If you plan to travel overseas consider buying a tri or quad band phone here and when in another country, say Italy or Russia... buy a SIM card in that country for $20 or whatever minutes you want, then pop their SIM into your phone to make calls. If you rely on CIngular or any other US carrier they will screw you over for international per minute fees. Two years agoI was in Ukraineand my cell bill with Cingular was $900 and that was just a two week vacation. My parents, also with Cingular, just came back from a Euro trip, had a $1500 cell phone bill. Cingular talks the talk as far as cheap international calls, but they dont walk the walk. They are ridiculus! Dont be afraid to ask a phone dealer in another country about buying a SIM card from them to put in your phone... it will save you TONS of money.