Okay kiddo, so you know how sometimes you need a safe place to go when you feel scared or threatened? That's kind of what a sanctuary is.
Imagine you're a little bird and there's a big scary cat chasing you. You fly as fast as you can but you're very tired and can't go any further. But then you see a birdhouse with a little sign that says "No cats allowed – safe zone for birds!" So you go in there and the cat can't get you anymore!
Now, people can also need a sanctuary sometimes. It's a safe and peaceful place where they can be protected from harm. For example, people who have been hurt or threatened by others might need a sanctuary where they can go to be safe and get help.
Sometimes, cities or churches will even declare themselves "sanctuary cities" or "sanctuary churches", which means they promise to protect and provide assistance to people who are in danger of being deported from the country or facing other forms of harm.
So, just like the birdhouse protected the little bird from the cat, a sanctuary can protect people from harm and give them a place to feel safe.