The invention of the Laser has provided mankind with an energy source which can be focussed to a very small spot size. Visible laser beams are used in metrology, voice transmission and a large number of scientific applications. Medium power lasers are used in the medical field, and High Power Lasers - from the 50 watt to 15,000 watt range - are gaining rapid acceptance by the Manufacturing Industry. This paper presents an overview of the principles involved and their current use.