WHAT they are: I started painting with oils recently which is why I decided to start with water-based.  The web site for the Artisan line from W&N is explicit and provides many answers to what these products are and how to use them.  It made my decision easier.  They are also environmentally good.  These are oils, the chemistry is only changed slightly to have a "tail end" which is water soluble; once the colors dry the oil remains and it has the same chemical features of standard oils.