A new chapter needs a fresh page. A wide table needs a landscape page. Both move content around, but only the second request changes the page layout. Choosing the right break saves a surprising amount of tidying later.
Move the text, or change the layout?
A page break starts the following text on the next page. It does not create a separate area for page orientation or other section formatting. Use it when the next chapter should keep the document's existing layout.
A section break creates a formatting boundary. In desktop Word, look under Layout → Breaks. Next Page starts a section on the following page; Continuous starts one on the same page, which is useful for changing the number of columns. Odd Page and Even Page can leave a blank page so a chapter starts on the chosen side.
Check both ends of the change
Imagine a portrait report with one wide table in the middle. In a copy, place section boundaries around that part, then change its orientation. Check that the text after the table returns to portrait. Turn on formatting marks first so existing breaks are visible.
Check headers, footers and page numbers too: a new section does not automatically make every element independent. Word for the web cannot currently add section breaks; use desktop Word for that change. Export the copy to PDF and inspect the page before the table, the table itself and the following page. Avoid pushing text down with repeated empty paragraphs.