Mobile Phone Features
-Single is just one country.
-Most phones have dual, which means that they can be used in all of Europe.
-Tri allows the phone to work in most other parts of the world.
-Quad works all over the world, in every country.
They're all affected by network coverage, not the phone. If you're a constant traveler it's better to get a quad band phone as it will ensure coverage by all networks in a particular country.