Why a picture instead of a word
A child of four does not translate. They do not see “frog”, think of a frog, then reach for la grenouille. They see the frog and say the word, and the English never enters it. That is the whole reason these cards carry a picture on the front: the detour through a first language is the slow part, and at this age you can simply skip it.
It also means a child who cannot read yet can use the deck alone. The picture is the question, the sound is the answer, and nothing in between asks them to decode letters. The English is there on the card for you, the adult, not for them.
How to use ten cards with a small child
Ten is deliberate. A four-year-old gives you about five minutes of real attention, and a deck of two hundred cards is a deck that gets abandoned on card six. Ten can be finished, and finishing is what makes a child want to come back tomorrow.
Play it out loud and take turns. Press Listen, let them repeat after Camille, then say the word yourself badly on purpose and let them correct you. Children learn a sound far faster when they are the one judging it.
Do not test. If they say the English, say the French back cheerfully and move on. Marking a card “Still learning” brings it round again in a minute, which is all the correction a child this age needs.
The ten words, and why these ten
One word from each of ten themes, chosen so the French is worth learning rather than guessable. La grenouille, le nounours and l'arc-en-ciel sound nothing like frog, teddy bear and rainbow, so they are real vocabulary rather than near-cognates a child would have got for free.
La maman, la maison, la voiture and les yeux are in because they are the words a small child uses twenty times a day. Learn those four and French stops being a school subject and starts being something you can say at breakfast.