在。net中，当我们编译源代码时，会在Visual Studio中生成程序集。程序集由清单和IL(中间语言)两部分组成。清单包含程序集元数据意味着程序集的版本要求、安全标识、组成程序集的所有文件的名称和散列。IL包含类、构造函数、主方法等信息。

看到这个:

在Microsoft .NET框架中，程序集是用于部署、版本控制和安全的部分编译代码库

MSDN给出了一个很好的解释:

Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment, version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources that are built to work together and form a logical unit of functionality. An assembly provides the common language runtime with the information it needs to be aware of type implementations. To the runtime, a type does not exist outside the context of an assembly.

维基百科说:

In the Microsoft .NET framework, an assembly is a partially compiled code library for use in deployment, versioning and security. There are two types: process assemblies (EXE) and library assemblies (DLL). A process assembly represents a process which will use classes defined in library assemblies. .NET assemblies contain code in CIL, which is usually generated from a CLI language, and then compiled into machine language at runtime by the CLR just-in-time compiler. An assembly can consist of one or more files. Code files are called modules. An assembly can contain more than one code module and since it is possible to use different languages to create code modules it is technically possible to use several different languages to create an assembly. Visual Studio however does not support using different languages in one assembly.

如果你真的浏览过，澄清你不理解的地方会有帮助

用更简单的术语来说:可以由. net运行时环境执行的(预编译的)代码块。. net程序由一个或多个程序集组成。

物理集合类，接口，枚举等，这是在IL代码。可以是。exe或。dll文件。exe是可执行文件，. dll可以在任何。net支持的语言中动态使用。