It's a statement taken by the Gardai or prepared by a victim of a criminal offence which details the physical and/or emotional harm caused by the crime tried and any damage or loss to property suffered by the victim.
The statement can only ever be put before the trial judge after the accused has been found guilty but before he is to be sentenced.
There is no statutory basis for them in this jurisdiction save for the Criminal Justice Act 1993 which has a section stipulating that the court must take account of the impact a particular crime had on the victim.
The only crimes that this relates to are sexual and violent ones though.
Hope this explains.