Your child will already have some practical knowledge understanding of 'nothing there' or 'all gone'. During this unit of work they will learn that the number name zero and the numeral 0 can be used to represent this idea. Your child should be given opportunities to apply this understanding within the classroom or in this case whilst at home. E.g. There are no biscuits left on the plate. Numbers songs which count back to develop the understanding that 0 is less than one.