OpenVPN - Definition from the Hotspot Shield Glossary
OpenVPN (Virtual Private Network) is an open-source software application that is use for creating VPN’s. As OpenVPN is open-source it means that anyone has access to it and can modify the application as they see fit.
If you want to host VPN’s or redistribute the program in a modified form, you will need to obtain a license first. OpenVPN involves authentication using shared keys and the SSL/TLS protocols and is available on most widely used platforms including Windows, Mac OS, Linux and Solaris. Advantages of OpenVPN include aforementioned compatibility with a variety of operating systems, great speeds of around 1.4mbps, bandwidth management and the ability to maintain multiple connections at once.