1, the meaning is different:

Fuming sulfuric acid, that is, sulfuric acid solution of sulfur trioxide. Colorless to light brown viscous fuming liquid, its density, melting point and boiling point vary with SO3 content. When it is exposed to the air, the volatilized SO3 and the water vapor in the air form fine dew drops of sulfuric acid and smoke, so it is called fuming sulfuric acid.