Microsoft Knowledge Base Article 242468 contains the following summary:

Netsh.exe is a tool an administrator can use to configure and monitor Windows-based computers at a command prompt. With the Netsh.exe tool, you can direct the context commands you enter to the appropriate helper, and the helper then carries out the command. A helper is a Dynamic Link Library (.dll) file that extends the functionality of the Netsh.exe tool by providing configuration, monitoring, and support for one or more services, utilities, or protocols. The helper may also be used to extend other helpers.