- Countries (the phone will work in one country, but not another)
- Network/Service providers (e.g. AT&T Mobility, T-Mobile, Vodafone, etc.)
- SIM types (i.e. only specific SIM cards can be used with the phone).
In most countries, most mobile phones are shipped with country and/or network provider locks. In addition, these locked phones tend to have firmware installed on them which is specific to the network provider. For example, if you have a Vodafone or Telstra branded phone in Australia, it displays the relevant logo and may only support features provided by that network (e.g. Vodafone Live!). This firmware is installed by the service provider and is separate from the locking mechanism.
Most mobile phones can be unlocked to work with any GSM, such as O2 or Orange (in the UK), but the phone may still display the original branding and may not support features of your new carrier. Most phones can be unbranded by uploading a different firmware version, a procedure recommended for advanced users only.
