Entertainment (read: casino) company. They have casinos in Reno, Lake Tahoe, Las Vegas, and Laughlin, Nevada, New Orleans, Louisiana and Atlantic City, New Jersey. Not to mention various riverboat and Indian reservation casinos. Their most notable properties are Harrah's Las Vegas, the Rio, and the Showboat riverboat casinos.
IMHO, a pretty good investment for someone interested in the gaming industry. They're well diversified in many different markets, and focus on service and increasing revenues at existing properties rather than sinking astronomical sums into new casinos like some people *cough* Steve Wynn *cough*. Oh well, that's why it's MGM Mirage instead of just Mirage now. Maybe Bellagio wasn't the most prudent investment. But I digress.