public class Branch : ContainerModule, IModule, IModuleList, IList<IModule>

Assume you have a module, AddOne, that just adds 1 to whatever numeric value is in the content of the input document(s). The input and output content of the following pipeline should demonstrate what Branch does:

                    // Input Content      // Output Content
Pipelines.Add(
    AddOne(),       // [Empty]            // 0
    AddOne(),       // 0                  // 1
    AddOne(),       // 1                  // 2
    Branch(
        AddOne(),   // 2                  // 3
        AddOne()    // 3                  // 4
    ),
    AddOne(),       // 2                  // 3
    AddOne()        // 3                  // 4
);

You can see that the input content to the AddOne modules after the Branch is the same as the input content to the AddOne modules inside the branch. The result of the modules in the Branch had no impact on those modules that run after the Branch. This is true for both content and metadata. If any modules inside the Branch created or changed metadata, it would be forgotten once the Branch was done.

This allows a sequence of modules to execute without impacting the "main" module sequence. In other words, Branch executes it's child modules as if there were no Branch module in the sequence, but then when it's child modules are done, the main sequence of modules is executed as if there were no Branch.