Okay kiddo, have you ever seen a tiny seed that turns into a flower or a fruit? Well, just like that, a zygote is like a tiny seed but for humans, animals and many other living things.
Let me explain further, when a mommy and a daddy love each other very much (or when animals mate), the daddy gives the mommy a special cell called a sperm and the mommy gives the daddy another special cell called an egg. These cells join together inside the mommy's body and they form a zygote.
The zygote is like a magic potion that has all the important things that a baby needs to grow. It has instructions on how to make eyes, arms, legs, and all the other parts that make us human or any other kind of living thing.
At first, the zygote just floats around inside the mommy's body, moving from the fallopian tube to the uterus, until it finds a cozy spot to stick and grow into a tiny little human or animal. As time goes by, that tiny little human or animal gets bigger and bigger, until it's finally born!
So, that's what a zygote is, a tiny seed that has all the instructions to make a baby or animal, and it's formed when a sperm and an egg join together.