A .net program can be written in multiple languages like c#,vb.net etc. it is necessary to have compatibility in types while communicating between programs/assemblies written in any of thease languages.common type system (cts) specifies the standards for type definitions across .net languages. for example an int32 in c# is equivalent to an integer in vb.net.

Assemblies are known as the building blocks or the fundamental parts of a .net application.
an assembly can be an exe (process assembly) or a dll (library assembly). they are the basic or the smallest unit of deployment.

there are two kinds of assemblies - private assembly, public or shared assembly

A namespace is a logical grouping of related classes which helps to distinguish classes with same name. for example system.io namespace contains a set of related classes which are useful to perform io operations

A namespace is a logical grouping of related classes which helps to distinguish classes with same name whereas an assembly is a physical grouping of logical units

an assembly may contain multiple namespaces

A manifest is a file which contains metadata information about an assembly. a manifest contains the below information’s
1) name of the assembly
2) version of the assembly
3) file list
4) public key token (strong name)
5) culture
6) referenced assemblies

A global assembly cache is a central repository in a machine where all the shared assemblies which are intended to be shared across multiple applications will be stored. usually a gac will be stored at c:\winnt\assembly or at c:\windows\assembly. an assembly can be installed to gac using gacutil tool. gac is introduced to avoid problems like dll hell. assemblies which has a strong name are only allowed to be installed in a gac