Ok kiddo, so garde manger is a fancy French term that means "keeper of the food." It's a special job in fancy restaurants where the garde manger person makes all the cold and pretty food like salads, charcuterie (that means meat stuff like ham and salami), and other fancy appetizers.
So imagine you're at a really fancy party with lots of adults, and there are lots of small plates with pretty food on them. That's probably all made by the garde manger person. They have to be really good at cutting and arranging food in a way that looks nice and makes people want to eat it.
It's kind of like being an artist, but instead of using paint or clay, they use food. And just like an artist, they have to practice a lot and learn new techniques to get better at it.
So that's what garde manger means! It's all about making beautiful and delicious cold food for fancy restaurants and events.