The newer designation of "E-Band" lies in the extremely high frequency bands from 71 to 76 gigahertz (GHz), 81 to 86 GHz and 92 to 95 GHz. It is being used for short range, high bandwidth communications. 
At these high frequencies the short wavelengths give the radiation a very directional quality, similar to visible light. Many molecules possess rotational and vibrational states excited by very specific wavelengths in this band, thus the atmospheric gasses such as oxygen, water vapor, carbon dioxide and nitrogen can absorb, and be excited causing variable beam attenuation effects dependent on meteorological and atmospheric conditions.
The microwave spectrum is usually defined as electromagnetic energy ranging from approximately 1 GHz to 100 GHz in frequency, but older usage includes lower frequencies. Most common applications are within the 1 to 40 GHz range. Microwave frequency bands, as defined by the Radio Society of Great Britain (RSGB), are shown in the table below:
Footnote: P band is sometimes incorrectly used for Ku Band. "P" for "previous" was a radar band used in the UK ranging from 250 to 500 MHz and now obsolete per IEEE Std 521, see and . For other definitions see Letter Designations of Microwave Bands