I think the simplest way to put it is that people become unable to not look at porn and masterbate, it feels like you have no choice, it’s a thing you must do even if it is ruining your relationships, could potentially also wreak havoc on your career, even finances if you get sucked into the cam sites.
If you feel like you can’t get through the day without it, it might be an addiction. There is a quiz on the sa.org website to help people figure it out too.