NAT- Firewall Rule

[rl82]

Good morning,

I have a question.

I set up a 1: 1 NAT with a machine in the internal network that should send requests to a remote machine over the internet (a kind of web server).
I proceeded to create a virtual IP and to properly set the NAT 1: 1 and the outbound traffic.
Based on the material I found on the internet, I read that this is not enough as you also need to put a Firewall Rule. Could you kindly give me more info about it because I couldn't find much.

Thank you

Have a nice day