Unlocking smartphones?

Question

i have been looking through the cell phone questions and i have been seeing things like you have to unlock the phone with a carrier. i do not understand that at all the whole unlock thing. can someone please explain? thanks (:

Answer 1

When a company like T-Mobile sells a phone to one of its customers, that phone has a subsidy lock installed in it so it can only be used on the T-Mobile network. When you unlock the phone, it can be used on another netwrok like AT&T.

Only GSM phones can be unlocked to use on another network. GSM phones use sim cards.