You can zoom into any corner of this 8K photo online and still see the details of the picture. Let's put this concept to the audio to explain high resolution audio. High resolution audio content include extra high frequency information. As shown below. The differences won't be noticed until you play the audio in the large theaters or the high quality amplifier sound systems. In those cases the audio gets largely amplified or you can say zoomed in.
The most popular high resolution audio format is DSD audio. DSD stand for Direct Stream Digital audio. It is a new hot topic on the audio enthusiastic nowadays.
What is DSD different to normal digital audio?
The best example to explain this technology is to use analogue recording tape. The idea of DSD is to digitally recording sound use analogue approach. The analogue audio recording is the linear recording technology. This approach has been used since the beginning of the audio recording. The method is simply sample the sound directly in the linear order. For example the vinyl recording. The machine writing the sound directly on the vinyl disk continuously until the music stopped. This is the same approach DSD used. Because it is the digital process without need for actual moving mechanical parts. The DSD recording result is fascinating on the sound quality without noise.