In Word, a break is automatically added at the end of each page. You can also insert a manual page break if you want to start a new page in the document. For example, if there is a part of your text that you want to start on the next page, or a table that fits on a full page rather than the table being split into two pages, you can insert a page break to keep the table on a single page.
See further instructions on Microsoft's website: Insert or delete a page break.
Use section breaks with caution. If you are not careful, page numbering, margins, and page size may change after you insert a section break.
Insert section breaks when you want to change the layout of the page. For example, if you want a section with larger margins, or if you want pages in landscape view. That is why there is a section break after the Abbreviations page. None of the pages before the section break have page numbers, and numbering starts after the section break (on the Introduction page).
Tip: If Word unexpectedly places a new page in the document, it may be due to a page break. If you want to make page breaks visible, or if you need to highlight and remove them, go to Start > Show/Hide icon.
See further instructions on Microsoft's website: