Definition - What does Terahertz (THz) mean?
Techopedia explains Terahertz (THz)
Terahertz radiation has a hard time penetrating fog and clouds and cannot penetrate liquid water or metal, which makes its use quite limited to indoor environments. It is also non-ionizing, which means it does little to no damage to living tissue. This also means that there is no immediate need to make use of the frequency for a wider audience, such as in telecommunication, because of its drawbacks, but it may find many uses in other fields such as medical imaging because of its non-ionizing properties.