The court when sentencing will consider prior offences the defendant has committed. Of particular importance are the ones that are similar in nature to the offence they are being sentenced for. For example, if the offence they are being sentenced for is theft, then all offences involving dishonesty are most relevant.
The prosecutor will tell the court of any offences that have been proved against the defendant in the past. These may include matters which the person committed as a youth and also matters where no conviction was recorded but the charge was proved. Although, family conferences and informal or formal cautions as a youth are not considered to be prior offences for sentencing purposes.
The defendant should been given the details by the prosecutor of what they intend to provide to the court, and the defendant should check them for accuracy before they tendered as evidence in court.