GAC stands for Global Assembly Cache
Role is to store some public Assembly have a lot of programs to be used, for example, System.Data, System.Windows.Form and so on. In this way, a lot of programs you can get inside the Assembly from the GAC, then all without the need to
Used in the Assembly are copied to the execution directory of the application below.
C # DLL registered to use the DLL in the GAC and add references
Reference: https: //blog.csdn.net/World3000/article/details/81983590