MetaData
Metadata is aset of data tables that describe what is defined in the module, such as types and their members.
MetaData also has tables indicating what the managed module references, such as imported types and their members.
Assembly?
An assembly is a logical grouping of one or more modules or resource files.
An assembly is the smallest unit of reuse, security, and versioning.
In CLR workd, an assembly is what we would call a component.
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原文：http://www.cnblogs.com/sift/p/3594732.html