"Mortalium animos" is a Latin phrase that means "the souls of mortals".
Imagine that you are a little bird looking down on people walking around in a big city. Each person has a soul - it's like a special magical part of them that you can't see, but it's there. Sometimes people believe in different things, like different religions or ways of living, and this can cause disagreements and problems.
"Mortalium animos" talks about how people should try to respect and understand each other's beliefs, even if they don't agree with them. It's like saying, "just because we have different souls, it doesn't mean we can't be kind and understanding to each other."
So basically, "mortalium animos" is about being open-minded, respectful, and tolerant of others, especially when it comes to their beliefs and ways of living.