Mouros is a word that is often used in Portugal to describe a type of mythical creature. These creatures are said to be tall and dark with glowing eyes, and are said to have magical powers.
Think of them like monsters in a storybook. They are imaginary, but people used to tell stories about them to scare children or explain things they couldn't understand.
People in Portugal may use the word mouros to describe anything mysterious or unexplained, kind of like how you might use the word "spooky" or "creepy" to describe something that scares you.
So basically, mouros are just mythical creatures that people used to talk about a long time ago to make things seem more interesting or to explain things they couldn't understand.