There are 3 common or main lasers on the market today.
Co2 Laser
The carbon dioxide laser (CO2 laser) were the earliest gas lasers to be developed and offer a high power continuous wave of infrared light. The glass tubes are relativley big and need a specialized gantry or frame builts on the cnc to house the tube. The beam is then reflected via quality mirrors and focused to a fine point though a lens to the job suface. These lasers come in a variety of different sizes and power rating which enable them to cover cutting a very wide range of materials and alse engrave on them. To see what types of materials a Co2 laser can cut and engrave, click here.
YAG Laser
These lasers come in a wide rage of power levels and predominantly used for metal cutting
Fibre Laser
One of the newer technologies, fibre laser cost far more to setup but are very low maintenance and cost less to servie when compared to YAG lasers. Fibre lasers also are used mostly for metal cutting.