Assembly

Assembly is the smallest unit of deployment of a .net application. It can be a dll or an exe.

There are mainly two types to it:

Private Assembly: The dll or exe which is sole property of one application only. It is generally stored in application root folder

Public/Shared assembly: It is a dll which can be used by multiple applications at a time. A shared assembly is stored in GAC i.e Global Assembly Cache.

Moreover follow the link:

https://msdn.microsoft.com/en-us/library/hk5f40ct(v=vs.90).aspx