Some of the benefits of having an unlocked international phone include the ability to swap networks as needed, lower roaming costs and increased long-term savings. Unlocked international phones owe these advantages to their ability to use SIM cards from different networks without restrictions.
Unlocked international phones take advantage of the Global System for Mobile Communication standard, a mobile telephone systems standard that originated in Europe and has become the most widely used wireless telecommunications standard in the world, as of September 2015. In comparison to CDMA phones, which are popular in the United States, GSM phones use SIM cards rather than built-in electronics to store network configurations and subscriber information. Locked phones only work with specific SIM cards, but unlocked phones can use SIM cards from any network.
This characteristic allows users to swap networks by buying separate SIM cards from different networks so they can choose whichever network works best at a particular location. For example, if a subscriber has good AT&T coverage at home but suffers from loss of signal at work, he can switch to T-Mobile after leaving the house so as not to lose coverage. This gives international travellers the ability to avoid high roaming costs by purchasing and using a SIM card from a local network in their country of destination.