They're mostly dead - which means they look normal, unless they don't want to.
A Ghoul is a human who drinks Vampire blood without first being drained. They become slightly mind-controlled servants of their Vampire masters, but also acquire some Vampire abilities (supernatural strength and speed) without giving up the ability to walk in sunlight. They also become immortal (though not invulnerable) so long as they get regular supplies of Vampiric blood to drink.
Adam Selene was a Ghoul soldier in the Tech Infantry, and Fabian Cortez is a high-powered Sabbat ghoul in the service of Mordred.