That’s a manual pipe threader / pipe threading machine
Specifically it looks like a Ridgid-style ratchet pipe threader die head.
What it’s used for:
1. Cutting threads on pipes - It cuts screw threads onto the end of metal pipes like galvanized steel, black iron, or stainless
2. Plumbing and pipefitting - Used to make threaded pipe for water, gas, oil, air lines
3. Repair work - If a pipe thread gets damaged, you can re-cut new threads with this