Carlos felt a little surge of guilt at h er quick agreement. He wasn't explaining things all that well. There were so many things that were second-nature in his world, but he couldn't possibly expect her to just accept and understand them without question.
"In my world and I would hope here, the threshold of your home has a power. Home is your source of power. It's where your memories are, your identity, your life. Creatures and those with magical powers need an invitation to cross that threshold. If you don't grant it, many can't come in at all. Those who can leave a good deal of their power at the door. Refraining from that verbal invitation keeps that barrier up between you and them. Once it's offered, they are free to enter and bring all their power and potential malice with them."
He stopped and studied Mag to see if she would understand or if she might have further questions. He realized that there were quite a few things that he wanted to explain to her.
"I can't promise that everything in this world works in the same way as my world, but I would imagine that enough of them do that taking precautions should increase your chances of safety quite a bit."