Okay kiddo, so a fichu is a piece of clothing that people used to wear a long time ago. It's like a small scarf that you wear around your neck and shoulders.
Imagine it's a cold day outside, and you want to keep yourself warm. You put on a jacket, maybe gloves, a hat, and maybe a scarf around your neck. But what if you don't want to wear a big, heavy scarf? That's when a fichu comes in handy.
It's smaller than a regular scarf, so it's easier to wear. You can put it on over your shirt and it will cover your neck and shoulders. It's not as warm as a big scarf, but it does help keep you a little bit warmer.
People used to wear fichus a lot in the olden days, especially women. They would wear them with fancy dresses and they could also wear them as a kind of shawl to cover their arms if they were wearing a sleeveless dress.
So a fichu is a small scarf-like piece of clothing that people used to wear to keep their neck and shoulders warm or as a fashion accessory with fancy dresses.