Shift work is common in many industries, because of the hours which need covered. In tourism, food and drink, manufacturing or health and social care you can expect a shift pattern. You might be dealing with global clients in different time zones or customers who expect service out of office hours.
It just means your hours run over certain times each day or week. You might follow one pattern one week and a different one the next. Some shift work also involves working nights. There are special rules around night working hours and you can find more information on this on gov.uk.
Offshore workers can be away from home for weeks at a time, working different shift patterns.