Welding and the occupation of a welder?

Welding is fusing two metals together. Welders do the welding.

Welding is the melting of two metals and also sometimes the addition of extra metal to make up for shrinkage that occurs in the process.

With "heat" caused by gas or electricity or both the welder creates a small pool of melted together surfaces and then moves this small puddle in circular or "S" shaped patterns until the weld is complete. Controlling the heat and puddle is crucial to good penitration and thusly a good weld.

welders do not "glue" the two surfaces together, they melt them.