An unlocked handset is simply one that you can put any sim card into and make a call. SOME operators lock their handsets so that you can only use their sim card, but not all do this.

Its relatively cheap to get one unlocked - cheapest I've seen for the Ericsson here in UK is £4.99. You can do it yourself, but you'll need software and a data cable - its probaby cheaper to pay someone to do it locally, or just buy it already unlocked.

A brand new handset from anywhere should already be unlocked - if its in an Ericsson box, its probably ready to accept any sim. Be careful buying a phone on Ebay, if it ever gets reported stolen by the seller, the serial number will be blacklisted, and it'll be useless.