A hotel or group of hotels together with casinos, convention facilities, entertainment facilities, museums, theme parks, retail and dining.
Marina Bay Sands in Singapore is often used as a reference for what a Japanese IR will look like.
In Japan, Odaiba (Tokyo) or Minato Mirai (Yokohama) are two examples of areas that have similar types of facilities in an area more expansive than a typical IR, excluding the of course the casino.