The Yahoo! Voice services are based on VoIP technology. VoIP is just a fancy acronym meaning "Voice over Internet Protocol." When you travel, you can make calls using Yahoo! Voice as long as you have an Internet connection and the newest version of Yahoo! Messenger with Voice. If you're traveling to the desert or plan on hibernating in a cave, then you will not be able to use Yahoo! Voice services. If you're in the desert or cave and have an Internet connection, then you're one wired person.