Most corporate, school, or hotel Wi-Fi networks implement strict firewalls. These firewalls typically block unknown UDP ports (like 1194, the default OpenVPN port) but must allow UDP port 53 outbound to the internet. Why? Because without DNS, no one could access google.com or any website.
The "vpnbook com openvpn udp 53 zip" refers to a configuration package provided by VPNBook that includes settings and certificates necessary for connecting to their VPN servers using OpenVPN over UDP on port 53. This configuration is usually distributed as a ZIP file, which contains: vpnbook com openvpn udp 53 zip
Add these lines to your .ovpn file: