Every assembly maintains version information in two forms, identity and informational. The version number, name, and culture of the assembly form the identity of the assembly and the informational version is provided in a string format specified in the assembly info file and is for informational purposes.

The version number of an assembly is represented as a four-part string:

<Major version>.<Minor Version>.<Build number>.<revision>

For example, if an assembly version is set to 2.1.1234.2, this indicates that the major version of the assembly is 2, the minor version is 1, the build number is 1234, and the revision number is 2. When this version is created or updated, it is maintained in the manifest file along with a snapshot of all resources and dependent assembly files and their versions. In addition to this, versioning checks are applicable only when the assembly is signed.

One important thing to understand from a real-world scenario is that, when you build a product and release your assemblies for customers and later upgrade your assembly, then you have to maintain the previous versions. So, when a new version of an assembly is released, clients can still use the old version as long as it is supported.