How do I talk to little kids?

I don't know how to talk to kids, like how other people talk to them. I don't know whats age appropriate baby language or how to handle a kid situation. One time this kid was listening into what I said and honestly didn't know he could understand what I was saying. I kind of want to be a mom, maybe in ten years or so, but idk how to teach them things or whats appropriate to tell them or what or what they don't understand.