An unlocked phone is one that is not tied to any particular mobile operator, such as Vodafone or EE. Buying 'unlocked' usually means buying the phone outright without a SIM card or contract attached. The most important point is that an unlocked phone is almost always a better deal than buying a phone on contract - if you can afford it. The only real exception to this is Apple's iPhones - because of their traditional popularity, operators often subsidise the cost of buying an iPhone in order to lock you into a lucrative long-term deal. Generally speaking, if you can afford the upfront cost of the handset, you will pay less over the life of your phone by buying unlocked. More importantly, you are not locked into a lengthy contract. If you want a new handset at any time, you can buy one without having to up-purchase your way out of said contract or commit to another two years.  Just be sure to make certain the phone you're getting is not locked to a certain network.