OpenVPN is an open-source software application that allows users to create secure point-to-point or site-to-site connections in routed or bridged configurations. It uses a custom security protocol based on SSL/TLS for key exchange, providing a high level of security for data transmission over the internet. This software is widely used for creating Virtual Private Networks (VPNs), enabling users to access the internet securely and privately. OpenVPN can be configured to run on various operating systems, including Windows, macOS, and Linux, making it a versatile choice for both personal and business use.