This page is not definitive on the subject of immunity. In certain circumstances, the issue of whether immunity applies can be heavily fact-laden.
Immunity protects whoever has it from prosecution in a civil or criminal case.
A constitutional attorney has written that judges are vulnerable. Neither the politics nor economics of law practice permits lawyers to pursue such cases nor makes them affordable except to a small elite of citizens. Essentially the legislature concluded, Hey, if we require them to report a case child abuse or rape of child only even if its only a hunch, we cannot allow the accused person to sue the reporter if the hunch wasn't a good one. Not all statutory immunity is absolute. District attorneys and assistant district attorneys have qualified immunity, which means sometimes you can sue and sometimes you cannot sue them.