{fancyhdr} is a package which allows the creation of custom page headers and footers.
fancyhdr is a package which allows the creation of custom page headers and footers: it allows you to specify the contents of the left, right, and center of the header and footer on a page where \pagestyle{fancy}
is in effect. If your question is about headers and/or footers more generally, there's also the header-footer tag.
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