When you are using the Week view plugin, this display option defines whether or not weekends show up in the week table. Disabling weekends makes the table 2 days shorter and more usable on narrow screens. Weekends option for Week view
Below is a screen showing a week view with enabled weekends. The week table consists of 7 columns for workdays and weekends. Week view with enabled weekends
Compare it with only 5 days long week table below when weekends are disabled. Week view with disabled weekends
If your time records are mostly on workdays, consider disabling weekends in week view to optimize data entry. Note that Weekends configuration option applies only to weekends, not mid-week holidays.