Emax is a brand of lithium disilicate porcelain. An Emax crown can be made in 3 ways:
A wax pattern of the crown is converted into a mould into which a liquid mixture of the porcelain is injected under pressure. This method produces the best fit and is the most labour intensive.
CAD CAM (Computer Aided Design and Computer Aided Milling)
Premade Emax blocks are fed into a milling unit and a computer-guided drill cuts out the crown from the block based on a virtual 3D design of the crown. The 3D design is made from a mould or a 3D scan of the tooth.
The milled crown needs firing and glazing before it can be fitted.
Combining a pressed/CAD CAM coping with layering
The base layer of the crown (the coping) can be layered with different shades and translucencies of porcelain (lithium disilicate or feldspathic) to reproduce natural tooth features and make the final crown very lifelike. This is useful when the tooth to be crowned has a very dark colour that needs masking, since a very opaque coping can be used while keeping the final crown translucent in the right places.
Please see what zirconia and PFM crowns are like in my other reply here.