I'm new to Christianity and I'm trying to learn about everything but I don't have anyone in person to ask. One thing I'm confused about is the devil, satan, demons, etc. Is there anyone who has been explained what they are from a biblical perspective? Like is the devil one guy in hell? Is he in the world with us and presents as demons in people when it comes to people doing bad things? Is the devil one guy who sends demons out? Is there multiple devils? I just don't get it and I feel like in order to fully understand God and Jesus's sacrifice I need to understand the other side of it and what it is supposed to be. Sorry if this is a weird question. And why can't God stop him? Is it because people have free will and satan damages the world through actual people?