Difference between OpenVPN and VPN payment service

[Tradov]

Hello,

I have questions regarding the difference between OpenVPN and a commercial VPN service such as ProtonVPN or NordVPN.

Both are necessary, do I have to install OpenVPN and then hire a company like ProtonVPN?

Excuse me if I ask something obvious, but I have not been able to find the difference.

Thanks for your help.