VPNs provide flexibility, scalability, and lower costs compared to traditional private networks. A VPN allows connectivity on a shared infrastructure like the internet while maintaining private network policies and performance. Common types are access VPNs for remote access, intranet VPNs for connectivity between corporate offices, and extranet VPNs for connections to business partners. VPNs use tunneling and encryption protocols to securely transport network traffic across public or untrusted networks.