How the hell do VLANs work

https://imgur.com/a/PIJR8UW

I spent the last 5 hours or so trying to figure out why OPNSense won't properly connect to the subnet I set up for my proxmox nodes at 10.0.0.1/27 when I'm on 192.168.1.1/28.

While the settings aren't there anymore, I tried creating a Linux VLAN on .10, but NOTHING I could do on Opnsense's side would let me ping that motherfucker. Do I even need to be tinkering on Proxmox's side w/vlan awareness and other things, or is that solely for within proxmox?

I feel retarded.

E: So the answer was basically creating a linux VLAN on the proxmox node, setting the IP + gateway to that, adding a vNIC to the VM/CT which is tagged for that traffic, and then creating a VLAN in Opnsense, assigning that VLAN to an interface and assigning it the same IP range. Also had to fiddle a little with my smart switch.

Not fun. But learning.