What is global assembly cache GAC?

Global Assembly Cache :-- Assemblies can be shared among multiple applications on the machine by registering them in global Assembly cache(GAC). GAC is a machine wide a local cache of assemblies maintained by the .NET Framework.
We can register the assembly to global assembly cache by using gacutil command.We can Navigate to the GAC directory, C:\winnt\Assembly in explore. In the tools menu select the cache properties; in the windows displayed we can set the memory limit in MB used by the GAC