It is a type of electric furnace that is a transformer where the primary are the coils connected to the electric grid and the secondary the mass of metal to be melted.
The advantage of these furnaces are the high efficiency because heat is generated only in the mass to be melted, the electromagnetic currents agitate and homogenize the molten bath and have a quick start up because it hardly requires preheating.
However, the disadvantage is that no metallurgy is performed in the bath during melting.