Deferred Revenue Expenditure is an expenditure which is revenue in nature and incurred during an accounting period, but its benefits are to be derived in multiple future accounting periods.
These expenses are unusually large in amount and, essentially, the benefits are not consumed within the same accounting period.
Part of the amount which is charged to profit and loss account in the current accounting period is reduced from total expenditure and rest is shown in the balance sheet as an asset (fictitious asset, i.e. it is not really an asset).