Start_date argument is the date from which workday will be calculated. This date can be a working day or weekend, past day or future day.
End_date argument is the date to which workday will be calculated.
[holidays] Argument (Optional), Holidays argument is optional argument and used to excludes the holidays from NETWORKDAYS function output. We can give the complete range to exclude such days. Holidays are exception dates and such dates will not be counted as workdays (even those are falling on Monday to Friday)