it is a wave associated with particles revolving in an atom around nucleus. De broglie named these waves as matter waves or De Broglie's waves. its wavelength is calculated from wavelength λ=h/mv,
where, h is plank constant.
This theory mainly conveys the wave nature of light having energy given by plank E=hv. (v is frequency of radiation).
These waves do not require any material medium for it propagation. it is coming in mainly non relativistic theory.