water jet cutting can be divided into 2 categories:
Water Jet Cutting and Abrasive Water Jet Cutting
 
Both of the procedures require the water to be pumped to a pressure of up to 6000 bar, which is subsequently released via a nozzle, generating a high speed water jet.
Water jet cutting
Water Jet Cutting uses this jet as a tool to cut soft materials like foam, textiles  or food.
 
Abrasive water jet cuttting
When applying Abrasive Water Jet Cutting, an abrasive material is subsequently added to the water jet and accelerated in a focusing tube. The resulting abrasive water jet is able to cut all common technical materials, such as: 
steel and stainless steel
aluminum, non-ferrous metals and noble metals
chromium, nickel, titanium, tantalum etc.
hard metals
ceramics
glass, armoured glass
rock, granite, marble
sandwich materials, structural materials, reinforced plastics (CFK, GFK)
thermoplasts and duroplastics