OpenVPN is a famous and widely-used VPN solution, not only because it is open source, but also because it packs a large variety of handy additional features and functions. Its purpose, like pretty much all VPN tools, is to allow connecting to a VPN (virtual private network) in order to enjoy browsing the web while remaining anonymous and having the identity and the privacy well protected.
The OpenVPN client for Windows allows connecting to an OpenVPN server which enables hiding your real location and online identity. This client also offers a basic GUI (Graphical User Interface) that should make it easy to connect to a VPN and browse the web anonymously. Unfortunately it still relies on a config file that comes as an editable text file, so I find it rather difficult to see what advantages the GUI actually brings. It's not exactly cool for beginners to ask them to handle editable text-based configuration files, so the fact that it comes with a GUI doesn't make the OpenVPN client an easy-to-use tool.
Anyway, there are also a lot of benefits that this app offers. We're still talking, after all, about the most popular VPN tool in the world. Therefore if you use it you will be able to enjoy stuff like the possibility to tunnel any IP subnetwork or virtual ethernet adapter over a single UDP or TCP port, the access to the huge OpenSSL library of encryption, authentication, and certification features, the support for third-party plug-ins or scripts which can be called at defined entry points, and more.
In conclusion, it's easy to see why OpenVPN is so appreciated, but I personally consider that beginners will need to spend a couple of good minutes and learn the ropes before being able to properly set up and use this tool.