What does mDNS do? Because Ubiquiti's definition and Wikipedia's definition are very, very different.

Ubiquiti:
"Forwards mDNS requests across VLANs to enable service discovery between networks."
From their Learn More link: "transmit across different networks" and "forwards multicast traffic from devices between different networks (VLANs)". Seems like it's good for people who want to AirPlay from a phone on one VLAN to an Apple TV on another VLAN.

Wikipedia:
"Resolves hostnames to IP addresses within small networks that do not include a local name server."

Somehow I need mDNS turned on at a site where a Chrome user loses the ability to print to a wired printer. Both devices are wired, both devices are on the same VLAN, both devices have a static IP. Something something Chrome is looking for the printer as hpprinter.local instead of x.x.10.30 and mDNS is the fix.

Resolving hostnames and communicating across VLANs are very, very different processes, so which is it?