Summary
The Excel NETWORKDAYS helps to calculate the working days between two dates. This function automatically exclude the weekends (Saturday & Sunday). Whereas, this function have option to exclude list of Holidays.
Purpose
Helps to calculate the working days between two dates
Syntax
= NETWORKDAYS (start_date, end_date, [holidays])
Arguments
start_date: The start date
end_date: The end date
holidays: This argument is optional and have list of non-work days in the format of dates

Example Explanation
In above mentioned example we have showcase the working days from Jan 1, 2020 to Dec 31, 2020. In additions, we are excluding holidays from the mentioned dates. Formula used in Cells are:
Cell | Formula in Cell | Exclude |
D6 | =NETWORKDAYS(B6,C6) | Weekends only |
D7 | =NETWORKDAYS(B7,C7,$G$6:$G$7) | Weekends + Holidays |
D8 | =NETWORKDAYS(B8,C8) | Weekends only |
D9 | =NETWORKDAYS(B9,C9,G6:G7) | Weekends + Holidays |
Important Point
Networkdays include both start and end date while calculating working days.