A family of Microsoft word processing software products for creating web, email, and print documents.
When you insert a section break, each* header and footer of the section after the break is automatically linked to the corresponding one of the section before the break. To change that, you have to open the header (or footer) area by double-clicking in it -- so the Header & Footer Tools tab appears on the ribbon -- and click the Link to Previous button to turn it off. Only then will the headers/footers of the sections be independent.
* Every section can show up to three independent headers and three independent footers -- the main, first-page, and even-page headers/footers. The first-page header/footer show up when you check the box for Different First Page in the Header & Footer Tools ribbon. The even-page header/footer show up when you check Different Odd & Even Pages. When one or both of those options are turned on, the main header/footer becomes either the "second and following pages" header or the odd-page header.