Shader Cache is a GPU feature provided by driver's control panels, its reduces CPU usage in games and lowers the loading screen times in most video games, by saving the game data into your local Hard disk.
Note: This helps HDD users or any game stored an a HDD, SSD users already have amazing loading times like 2-3 seconds, so do these steps only if you have a normal 7200 RPM standard HDD. Make sure you have at least 50+ GB free space, so this feature can work more effectively. Its always a good choice leaving more free space in your HDD
NVIDIA users already have that features in their Nvidia control center for long time so its a good business decision made by AMD giving Amd users (finally) these options