You may be referring to column headings, which are always letters. They identify the columns.
They can be used to search for both letters and numbers.
That is not a function of Excel.
Excel :P
There is no reason why you cannot type that in. As there are letters in it, it will be treated by Excel as text.
XFD
dfdfsdfdsfdsfsdfsdf
I excel.
Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.Excel will automatically ignore cells with letters when averaging.
Column headings
column labels
They are short for "Excel Spreadsheet."
A font in Excel, MS Office, and all of typography is the style and size of characters (numbers and letters)