ARTISTIC is the term used to represent the traditional, narrow style wheel that is most thought-associated with roller skating.  The narrow shape makes the wheels lighter and much easier to maneuver when skating.  These wheels are used by the recreational session skater, the freestyle or rhythm style skater, or the competitive dance and figure skater.
 
Wheels are measured in 'mm' which represents the circumference of the wheel.  Smaller (45mm-52mm) wheels are for freestyle or rhythm skating, standard (57mm) wheels are for recreational or freestyle skating and tall (62mm) wheels are for dance and figure skating.

The hardness of the wheel will determine the amount of control you have.  A softer wheel (95a-98a) will "grip" the skating surface and allow for more control.  A harder wheel (101a-103a) will "slip" and give a more uncontrolled roll.