The .NET Framework provides two tools for working with the cache. One is a Windows shell extension that allows you to work with the cache using a Graphical User Interface (GUI). The other is a command line tool, called the Global Assembly Cache tool (Gacutil.exe), that is typically used in build and test scripts.
Global Assembly Cache
Abbreviated as GAC, the Global Assembly Cache is a machine-wide store used to hold assemblies that are intended to be shared by several applications on the machine. Each computer where the common language runtime (CLR) is installed has a global assembly cache. The global assembly cache stores the assemblies specifically designated to be shared by several applications on the computer.