As we see in the opening scene of the first episode, Goggins’ character is actually named Cooper Howard, who lived in the times before the nuclear holocaust that turned the planet into a wasteland. Like most ghouls, the residual irradiation deeply impacted Howard’s physiology. Over the years, then decades, a ghoul’s lifespan is greatly extended, but their bodies are deformed — their nose falls off and their skin turns zombie-like (though Goggin’s ghoul is still hot, which is important).
The ghoul is one of the most memorable elements of the “Fallout” franchise, serving as both antagonists and allies of the player character. They can retain their intelligence and humanity, and are no longer affected by most radiation or by most drugs — as seen when Goggin’s The Ghoul was completely unaffected by Lucy’s tranquilizer gun.
Not everyone in the wasteland turns into a ghoul in the games, but the show seems to hint that ghouls are this world’s version of zombies in “The Walking Dead” where everyone is doomed to eventually turn into a walker, based on comments from Lucy about eventually looking like Howard.
Though ghouls are still just humans, a lot of them fall into an animalistic, feral state. Their minds deteriorate by radiation, and they become actual zombies, as we see in episode 4 when Lucy is attacked by ghouls. In the games, ghouls go feral mostly due to social isolation, or mental breakdown caused by the trauma of the ghoulish transformation.
That’s not the case in the show, it seems. Throughout the season we see Howard use some kind of drug or serum. We learn that this is the only thing that prevents him from going feral, which may be a reference to the “Fallout 4” character John Hancock who is addicted to drugs.