[Elsie]

welder specific branch circuits are rated differently than other branch circuits in the NEC.

I did not know this.

I've just got a regular 220v line to the barn that I use. What's the difference?

[VTenigma]

Welder circuits don’t require a neutral and the wire gauge can be one size smaller. There’s more but it would be best to do an internet search for up to date info.