In Excel, subtracting an Earlier Date from a Later one will calculate the number of Days in between - which can be very useful.
However, we may need to calculate the number of Working Days between 2 Dates. If that is the case then NETWORKDAYS() is your go-to function. (Makes more sense if you read this as NET WORKDAYS and not NETWORK DAYS)
It excludes weekends plus has an optional argument that will exclude Holidays and other Non-working Days that you list in a Data Range.
NB! Just like any other Date calculations though, you need to work with genuine dates (auto-aligned to the right), otherwise this will simply error.
The default weekend for the NETWORKDAYS() Function is Saturday and Sunday. If you work Saturdays or have a completely different Weekend, then use NETWORKDAYS.INTL() which has an additional argument that enables you to set your weekend day(s).