What exactly does the charge "sexual assault of a child" include.?

There is a registered sex offender in the area and this was his crime. At the time of his arrest he was in his 40s and child 15. I would like to know exactly what ACTS someone must committ to be convicted of this crime, and is it a crime that is punishable by incarceration or could they possibly just do probation. Is there a website where I could find out exactly what this particular sex offender did to this child?