Take a look at these existing threads on this topic
The link that @cowski posted is the correct one. The other is confusing.
The magic words are "WCS is essentially a legacy object."
It does NOT stand for World Coordinate System. It is a temporary object that you can move around for legacy purposes. Because it is not associative, you want to avoid using it as much as possible.
For example, if you like to model using primitives, you might want to use the WCS to locate where the next primitive you create will be located.
It is also used as one possible method to orient Product & Manufacturing Information (PMI) annotation.
One of the first short-cuts to learn is to type the letter W to turn the WCS off (or on).
I was always tought "WCS" = "WORK coordinate system"
I.e. this csys you want to work in
Production: NX10.0.3.5 MP16/TC11.2
I'd rather be e-steamed than e-diseaseled
1) ABS is centered in the cube-shaped working space of NX.
2) Work Coordinate System: In any Information Window listing, when you see coordinate values that are of the format: XC = nnnn those numbers are based on the WCS, wherever it happened to be when the numbers were generated. So for a quick and intentionally non-associative verification, before you generate the Information Window, you can move the WCS to a location/orientation that would give you the values you are looking for. Additionally some dialogs present a Reference CSYS group where a drop down menu allows WCS as one option.
3) There is yet another legacy CSYS object in NX simply called a Coordinate System. Created via Menu->Format->WCS->Save it creates a non-associative (so it's not really used much) CSYS object at the location/orientation of the current WCS. This object can be used to snap the WCS to. Before parametric modeling users would create these CSYS objects all over the place in various locations so they could easily snap the WCS to them for various purposes. The same dialogs that present a Reference CSYS group with a drop down menu also offer a Select CSYS option where this non-associative legacy CSYS can be selected (along with the fully parametric Datum CSYS).