Why does proxmox have 2 ip address?

This isn't really a problem (or at least I hope so), I just want to understand proxmox better, but I didn't know where to ask this, and I didn't find any answers on the forum.
I was just messing with the router settings when I noticed, that whenever I turn on my proxmox machine, I have 2 more connected devices, not just one. They have different ip addresses (one of them is what I use to get to the web interface), but they share the same MAC address.
What is the reasion behind this?