1. *Welding metal* - Main job. The red + and black - terminals are for welding cables/electrodes. It runs on DC 140A, so it's for arc/stick welding. Used by fabricators, welders, construction workers for joining metal, repairs, gates, roofing, etc.
2. *Backup power* - See the "DC 220V" socket and "Auxiliary Output"? It also works like a small generator. You can plug in power tools, lights, grinders, drills when there's no NEPA/light. Rated power is 1.5kW DC.
Basically it's 2-in-1: welds + gives you electricity on site. That's why welders love it - no need for separate generator + welding machine.