The little prince of The Little Prince has been wandering around the desert for a few days when he meets a fox that wants to be tamed. "How does he know the fox wants to be tamed?" you ask.
Because it told him so.
Because it can talk.
Yeah, we're going to assume it's a magical fox. (Or the prince is hallucinating from the heat and dehydration). Whatever the case, after he tames the fox, the fox rewards him with a secret before he has to leave. The secret is this saying and the lesson it contains.
He's referring to something which confuses and pains the young prince: he had a very special rose on his home planet, but on Earth, he found many roses, making him realize his single rose wasn't all that special. But the fox knows that how we feel about something is what matters; in other words, the rose is special because the prince thinks it's special.
Sweet fox, eh?