The Adobe RGB (1998) colour space is designed to encompass the colours that can be output by CMYK colour printers.
When the RGB colour model is used on a modern computer screen, the Adobe RGB (1998) colour space aims to reproduce roughly 50% of the range of colours that an observer is capable of seeing in ideal conditions.
The purpose of the Adobe RGB (1998) colour space was to improve on the gamut of colours that could be produced by the earlier sRGB colour space, primarily in the reproduction of cyan-green hues.