What do people mean by an Unlocked phone?

Question

What exactly is an unlocked phone?

Answer 1

if your cell phone is unlocked it can be used with more than on wireless carriers. but many of people think that unlocking means just we do in our normal phones for security purpose. so unlocking the phones is different.

Answer 2

Generally when speaking of unlocked phones we are talking about a GSM phone. someone was able to get a code that unlocks the software. Once a device is unlocked, you can pop out the SIM card and put in a different SIM from another GSM operator and get service.