What is the O-2 visa? Is it true that it is can be used for persons accompanying an artistto the U.S.?

A: Yes. The O-2 visa is intended for persons who wish to come to the U.S. to accompany and assist an O-1 caliber artist or athlete who is set to perform a certain itinerary of upcoing events.  

The basic requirements of an O-2 visa is for the person to show:
(1) they are an integral part of the upcoming performance/event,
(2) that they have certain critically important skills and experience with the particular O-1 visa holder that are not of a general nature and which cannot be performed by other individuals, and
(3) that the applicant has a foreign residence which they have no intention of abandoning