OpenVPN Connect, the "official" OpenVPN Inc. app, is designed to be more user friendly for VPN users who have little technical understanding. This means that it is less featured than openvpn for android that is targeted at more advanced OpenVPN users.
Openvpn for Android is a free and open source client made by Arne Schwabe that allows you to connect to any VPN service that is compatible with the OpenVPN protocol. If your device doesn't support the pre-configured VPN apps available in the Google Play Store, this is a great alternative. The setup is pretty straightforward. You'll need to download the VPN profile files. (The configuration files are named.ovpn). These files can be downloaded from your VPN provider's site or by contacting live chat support.
After you've added your profile, click on the server to connect. Once connected you'll notice that your Internet traffic is routed via a secure channel to the server you've selected in the app. The Status tab lets you examine your connection's information and the status of your connection. A kill switch is enabled by Box cloud service default, and it will shut down your Internet connections when the VPN tunnel drops.
The application offers a per-app VPN as well as an always-on option that automatically creates an VPN connection whenever the app is opened and continues running even after your device has shut down or switched networks. However, this requires Android 7.0 or higher and can make your battery run more than usual.