Basics

Essentially DMX over ethernet or Wifi
Can replace bundles of dmx cables in applications with MANY dmx channels (or even universes) with a single ethernet cable
Can replace the cables entirely with wifi
Most off the shelf usb to artnet or artnet to dmx converters are expensive
Look into a rasberry pi sheild + code + case assembly for both use cases
Used mainly for stage lighting but could also be used if using dmx for robotics etc

Off the shelf converters/interfaces

An Artnet to DMX Converter ~275 USD (330 for POE)
Some models have multiple dmx outs as well
Artnet CAN be used on its own (assuming devices support the standard) and it can do some more complex things such as pixel led tape etc