What does it mean device is network locked?

What does it mean device is network locked? A network lock, known by many names including SIM lock, simlock, or subsidy lock, is a technology that wireless communications carriers use to prevent the mobile phones they sell from being used on another network. Cell phones can be locked to a particular country, network, or subscriber identity module (SIM) card.

A network lock, known by many names including SIM lock, simlock, or subsidy lock, is a technology that wireless communications carriers use to prevent the mobile phones they sell from being used on another network. Cell phones can be locked to a particular country, network, or subscriber identity module (SIM) card.