Does WHITE light ONLY include the wavelenghts betwen 390 and 750 nanometres or...?

White light IS all colors; (390-750) is the entire 'visible spectrum', so, if by "only" you mean 'all', yes. Not all 'electromagnetic wavelengths', just the Visible Light portion. Remember, the other 6 regions are also considered electromagnetic radiation - Radio, Microwave, Infrared, (here's VL), Ultraviolet, X-Ray, and Gamma Ray.