Any pattern of working time that covers five days a week.
However, within the five days, it is not necessarily the case that all 24hrs a day are covered; or the number of hours rostered a day is constant; or the number of people present on each rostered shift is the same.
The days not covered by the rota are frequently, but not invariably, Saturday and Sunday. The timing of the two days off can be from midnight to midnight, but more frequently it is linked to shift start and finish times. For example, from 22.00 Friday to 22.00 Sunday, or 06.00 Saturday to 06.00 Monday.