Forensic science is actually a bunch of things: science, engineering, even anthropology. But basically, it's the practice of applying scientific knowledge to legal problems. Forensic specialists may be scientists, lawyers, even anthropologists. There's even a group called American Academy of Forensic Sciences where you can find out about the specialties within the field.
The salary for this job varies; for example, a forensics lawyer may earn more than a forensics scientist. But an experienced forensics scientist can expect to earn between $40,000 - $85,000.