Theres a few reasons why you should know how to do this:

• Organization and Management:

  Master documents act as a container for multiple sub-documents (chapters, sections, etc.), making it easier to organize and manage long documents that would otherwise be unwieldy. 

• Collaboration:

  Different team members can work on separate sub-documents simultaneously, streamlining the collaboration process and ensuring consistency across the entire document. 

• Performance:

  Word processes smaller sub-documents faster than a single, large document, leading to improved performance, especially when working with very long documents. 

• Consistency:

  The master document can control the formatting, layout, and styles of its sub-documents, ensuring a consistent look and feel throughout the entire document. 

• Modularity:

  Sub-documents can be reused in other master documents, promoting efficiency and reducing redundancy. 

• Easy Updates:

  Changes made to a sub-document are automatically reflected in the master document, simplifying the updating process. 

• Smaller File Sizes:

  Breaking down a large document into smaller chunks can reduce file size, leading to faster loading and processing times.