What does an "unlocked phone" mean?

What does it mean to have a unlocked cell phone?

• I am searching on ebay for a new cell phone and I see that some phones say they are unlocked, what does this mean? Has anyone had any luck buying a new phone through ebay?

• Answer:

  Unlocked means that you can use that phone with any network that that phone uses. GSM unlocked network means you can use it with any GSM network, such as AT&T and T-Mobile. CDMA unlocked network means you can use that phone with any CDMA network, such as Verizon, Alltell, Sprint, and Cricket. Be careful with CDMA unlocked phones because CDMA phones do not use SIM Cards like GSM phones do, which means that some GSM phones that have been flashed to be used on a CDMA network have the software of a similar CDMA phone, so you could be missing some features. Hopefully you can get the jist of what i'm saying. Oh yeah, and ebay is a very reliable source for unlocked phones, probably one of the most reliable..just make sure the sellers feedback is good. Good Luck!!