what is the meaning of unlocked cell phone? And how do you do it?

A 'locked' cell phone is only usable with the provider that programmed it, eg, if you bought the phone from Cingular, you can only use it on a Cingular network.

If you have the phone long enough, or if you are nice enough to customer service (in this case, Cingular), they will give you an unlock code, which unlocks the phone to be used on other networks, provided it is compatible.

When someone talks about "unlocking" a cell phone they are referring to the fact that you can use the phone on any wireless carrier network.

So for example, if you buy a phone from Cingular, it will be locked to Cingular SIM cards. If you get the phone SIM unlocked, you will be able to put a T-Mobile SIM card into the phone and use it on T-Mobile's network.

There are a few stores in major cities that will unlock phones for you, as well there are many, many places on the net that will unlock your phone. For example (I have never used this) http://www.gsmlocker.com/

It means it is locked onto a partcular network and will only accept their sim cards. For example if i bought a T-mobile phone it will come with a t-mobile sim card and only accept t-mobile sims. What u need is a "subsidy pin" code which u get from ur service provider so it can accept any network sim cards when entered into the phone.