What does it mean by 'mobile phone unlocking'?

Question

Firstly how come a mobile phone gets 'locked'?

What does it mean?

Answer 1

Usually this refers to when a phone is bound or "locked" to a particular phone network. When you buy a phone, it will normally only work on one particular network. Phones can be "unlocked" to work on any network, either by contacting the network that a phone is locked to for an unlock code or by taking it to a phone repair/service shop or a local market place where they'll unlock it for you for a small fee. For some models of phone, the unlock codes can be found online.

Answer 2

Every mobile phone is locked when it is purchased new, say that it was purchased with a Vodaphone sim card in it it is locked to Vodafone, you can get it unlocked (meaning that you could use any simcard eg. TMobile, O2, Orange etc. You can ge this done by the network itself in a shop or search for the unlock code on the internet.

Answer 3

"[it] restricts the use of these phones to specific countries and network providers"