First, what’s an OpenVPN protocol?
OpenVPN is a free software, multi-platform, available on Windows, Mac OS, Linux, Android and iOS.
To secure your connection, the VPN (Virtual Private Network) you use, VPNFacile for example, has to use some tools allowing to make your connection private, that no third may seep your private network or access to your data between your device and the server to which you connect, for homeworking for example.
To do this, the VPN will use protocols, whose OpenVPN. We can imagine OpenVPN protocol as a private tunnel between your device and the server, to which you are the one that may access. This protection is possible because data that will transit in it will be encrypted thanks to protocols as OpenSSL or SSLv3/TLSv1.