Breaks create divisions within a manuscript. Two reasons are:

• Formatting reasons. E.g., Keeping paragraphs intact by moving them to the next page; and
• Separating content into distinct sections. E.g., Front matter, back matter, and chapters.

Breaks are preferred over the insertion of empty lines. The latter creates a cascading effect, which is difficult to manage in large manuscripts. I.e., End up with chapters starting at random points on a page.

Both types of breaks can be inserted under the Page Layout ribbon.