The information included in a criminal record and the existence of a criminal record varies between countries and even between jurisdictions within a country. In most cases it lists all non-expunged criminal offences and may also include traffic offences such as speeding and drunk-driving. In some countries the record is limited to actual convictions (where the individual has pleaded guilty or been declared guilty by a qualified court), while in others it also includes arrests, charges dismissed, charges pending and charges of which the individual has been acquitted.
It may be possible that your partner has never introduced you to his/her friends. Maybe he/she is avoiding it to provide his/her whereabouts. Maybe he/she hesitates to discuss the past. Possibly, you don't know where he/she works or worry that he/she lies about his/her work position or salary. There may be a chance of affair and abusive nature. On other hand, you are in a happy relationship and just want to sure that everything is fine. Whatever the reason for pre-Marital verification needs we work with dedication and commitment.