CNC meaning: Computer Numerical Control and has been around since the early 1970's.
Prior to this, it was called NC, for Numerical Control.(At the beginning 1970's computers were introduced to these controls, hence the name change.)
While people in most walks of life have never heard of this term, CNC is widely used in almost every form of manufacturing process in one way or another.
If you'll be working in manufacturing, it's likely that you'll be dealing with CNC on a regular everyday basis.