What is a worm drive in the computer and what is it's job?

A WORM drive is a write once, read many device. Various regulations require some types of information be recorded and be proven unaltered. Sarbanes-Oxley and HIPAA come to mind immediately. WORM drives provide a physical layer for compliance to these regulations.

In short, a Write Once, Read Many drive provides an recording for an unalterable stream of information. Once the data is written to the device it cannot be altered at the bit or file levels, only erased by destroying the volume.