They were a wrestling "gang" if I remember it correctly. I wasn't big into watching"professional" wrestling at the time, but I do recall that was a very popular group of wrestlers.
Wikipedia says: "The stable originated in World Championship Wrestling (WCW) with the gimmick of a group of unsanctioned wrestlers aiming to "take over" and control WCW in the manner of a street gang. The group later appeared in the World Wrestling Federation (WWF) after the purchase of WCW by the WWF.[2] The nWo angle became one of the most influential forces in the mid-to-late 1990s success of WCW and was instrumental in turning mainstream North American professional wrestling into a more mature, adult-oriented product. The stable became the main driving force behind WCW competing with the WWF in the Monday Night Wars."
Main members:
"Hollywood" Hulk Hogan (leader and co-founder)
Scott Hall (co-founder)
Kevin Nash (co-founder)
X-Pac (Hall of Fame member)