What is the value of the local $vhost_file variable when defined as $vhost_file = template("${module_name}/vhost.erb")?

The value of the local $vhost_file variable is derived from the use of the template function with the path to the specified ERB template file. When the template function is invoked, it processes the specified template file, which resides within a module. The phrase ${module_name} refers to the current module's name, ensuring that the correct template file is located based on the context in which the Puppet code is executed.

The result of calling the template function is not just a string representing the file path; it is, in essence, a function that generates the rendered content of the template file. This function returns the evaluated content of the ERB file as a string, which can include dynamic data and Puppet/Node-specific information, making the function itself functionally valuable.

Therefore, the assignment to $vhost_file effectively means that it holds the outcome of the template function—essentially a representation of the evaluated template, which is why the local variable is best understood as the template function's invocation that creates a dynamic string output based on the specified ERB template file.