There are various Attributes that you can apply to an assembly in the
form [assembly:SomeAttribute...]. These can be written into any of the .cs
source files in your project. However, if you spread your assembly
attributes over all of your files, it will be difficult find out what
attributes have been applied. This is why the project template provides the
AssemblyInfo.cs, so that you have a place to group together the assembly
attributes.
  Things that you may wish to specify there include the version of your
program, the KeyFile for strong-naming the assembly, various COM+
configuration properties for assemblies that use System.EnterpriseServices,
and many more.