The formula works by taking four arguments. The first argument is the start date whereas the second one is the end date. The third argument is the weekend day that can be selected out of various option described, here 1 corresponds to Saturday and Sunday. The last argument is the holidays that can be selected as range. Thus with this information the formula return the count of international net work days.
Category: Date and time
Returns the number of whole workdays between two dates using parameters to indicate which and how many days are weekend days
NETWORKDAYS.INTL(start_date, end_date, [weekend], [holidays])