High-Resolution Audio is audio that uses a higher sampling rate than in CDs and MP3s for the encoding and playback of music.
Listening to Hi-Res music allows you to pick up on the subtle details and nuances that you would hear in a recording studio.
This video helps you to understand what is different and how it enhances listening experience.

Sony High-Resolution Audio products let you hear music as the artist intended.
http://www.sony.net/Hi-Res