Okay kiddo, let's talk about the sounds that French words made long, long ago, and how they have changed over time.
A very, very long time ago, French people spoke a language called Gaulish. But then the Romans came and introduced their language, Latin, and a lot of people in France started speaking that. Over time, the Latin words mixed with some of the old French words, and the way the words sounded started to change.
One big change was that the Latin sound "k" became "ch" in French. So, the Latin word "casa" (which means "house") became "maison" in French. See how "casa" starts with "k" but "maison" starts with "ch"?
Another change was that a lot of Latin vowels became nasalized in French. That means that air comes out of your nose when you say some of the French words. For example, the Latin word "campus" (which means "field") became "champ" in French, and the "u" sound became nasalized.
There were also some other changes over time, like the "h" sound being dropped at the beginning of words, and some sounds becoming silent altogether. And that's how we got the way French sounds and the way its words are spelled today!