Ground-based gamma-ray astronomy

This paper provides a brief review of ground-based gamma-ray Astronomy. It is intended to discuss the basic observational techniques, technological co nstraints, and the advantages of going down in threshold energy. Some of th e major discoveries are listed - galactic and extragalactic. We discuss som e of the scientific returns as otained from observations of TeV sources suc h as the Crab nebula, shell remnants, and active galactic nuclei. Each sour ce provides us with a richness of new physics, which prompt us to built lar ger telescopes and better photon detection devices to go down in threshold energy, so that ground-based observatories can overlap in energy with space observatories.