The letter document class uses two different page styles for the first page depending on whether \address is used or not: firstpage if it is not used, and empty.
These headers typically contain document titles, chapter or section numbers/ names, and page numbers. according to document class (e.g., section name) and page number top right. The first line for the header, the second for the footer.
It may be worth noting that the headers and footers only appear from page 2 onwards. Although I've tried the fix for this given in the fancyhdr.
You can see more page styles in the next section empty: Both the header and footer are cleared (blank) in this page style. . top-level structure (for example, Chapter for reports and books classes; Section for articles) in uppercase letters.
to change page margings and sizes, headers and footers, and the proper Page 2 A page in a LATEX document is built from various elements as shown . In fact the standard LATEX classes have the command \maketitle.