This equation describes the imaginary portion (`kappa`) of the complex wavenumber1 (`tilde k`) of an electromagnetic wave in a conducting medium. `kappa` is a spatial angular frequency, normally given the units of rad/m. vCalc doesn't currently have any other unit options for angular spatial frequency, but feel free to request them using the "contact us" button at the bottom.
For more information on `tilde k` and how it's use, please refer to EM waves (attenuating) in a conductor.