Sub arc weld = "SUB"merged arc (like a mig shielded with flux)
Structural weldor = A person that is a structural steel weldor
B pressure = A person certified in a certain (B) pressure vessel weld ( just a guess)
Journeyman weldor = Someone who has "earned their stripes" (been welding some time and everyone goes to them for the answers)
Weldor = actual person who welds
Welder = machine that supplies the power to weld