Multi-Threaded Interactive Jobs?

A comment was posted to last week’s blog on IBM i Job Structures. It read:  

Dawn: This job structure article jogged my memory regarding a recent situation which I witnessed with an i customer. They have multi-threaded INTERACTIVE jobs running on their system. Can you sometime explain the concept of multi-threaded interactive jobs? I know and understand multi-threaded batch jobs but know nothing about multi-threaded interactive jobs. How are they created? What purpose do they serve? From a performance standpoint, does QPFRADJ adjust activity levels for multi-threads of interactive jobs? Any additional info would be helpful. Thanks!