What is Hell in actuality? How does it differ from the Underworld?

Hello Eric,
I have heard you speak of Hell and the underworld on a few occasions, but I also noticed you don’t seem to uphold the traditional viewpoint that Hell is a scary place underground where defiants of god are sent to perish in everlasting flames. I do not believe that theory either so I was curious.

From your own personal experiences via evocation, soul travel, and your opinions, what exactly is Hell? Is it simply another realm outside of the mundane physical plane where demons or other entities exist. Can it be accessed during soul travel, or is it a place that is only accessible by humans when given an invitation by a specific entity? Finally, what is the Underworld? Are Hell and the Underworld the same place, or are they two separate places that have simply been given similar connotations by society? Thanks!