Okay kiddo, so Yamato Nadeshiko is a fancy phrase that comes from Japan. Let's break it down: Yamato means Japan and Nadeshiko means a pretty flower called Dianthus superbus.
People in Japan use this phrase to describe a certain type of woman who is very beautiful and also very polite, graceful, and good at taking care of other people.
Imagine a princess from a fairytale who is always kind and gentle to everyone she meets. She might wear a beautiful kimono and have lovely long hair that she takes care of by brushing it every day.
So when someone in Japan calls a woman a Yamato Nadeshiko, they are saying that she is like a real-life fairy princess who is beautiful and also very nice to everyone she meets!