Borders are geographic boundaries of political entities or legal jurisdictions, such as governments, sovereign states, federated states, and other subnational entities. Borders are established through agreements between political or social entities that control those areas; the creation of these agreements is called boundary delimitation.
Some borders—such as most state's internal administrative border, or inter-state borders within the Schengen Area—are open and completely unguarded. Most external borders are partially or fully controlled, and may be crossed legally only at designated border checkpoints and border zones may be controlled.
Borders may even foster the setting up of buffer zones. A difference has also been established in academic scholarship between border and frontier, the latter denoting a state of mind rather than state boundaries.