Question

what is the The Rotating Magnetic Field?

Answer 1

Everything is in the name. What you might don't understand is : "what is a magnetic field". Actually it's nothing but a tool to represent the magnetism by "field lines" (I don't know if it's a right name in english). and vectors representing magnetism are tangent to these lines. why we use this representation ? Obviously because of the vector B (magnetism) is variable in space.
Now it's easy to understand what is a rotating Magnetic Field. Field lines of this magnetic field a turning around. Thus, magnetic Field is not only variable in space, but also with time.
When the professor speak about it, he takes the example of the rotating magnetic field in motor (asynchrony, or synchrony) where a magnetic field is create by different solenoids which are roughly supply not in the same time with an AC current. Therefore at one moment, the B in turning in the same axe of a solenoid, and in the next moment B is turning in the axe of the "next" solenoid. And etc.
I hope you understand what I'm saying, sorry for my english...