Okay kiddo, so vanilla milk is just regular milk that has vanilla flavoring in it!
Vanilla is a yummy smell and taste that comes from a bean. People can mix a little bit of that flavor into milk to make it taste sweet and delicious. It's kind of like adding syrup to your pancakes to make them taste better.
Some people really like vanilla milk because it's not as plain as regular milk, but it's not as sweet as chocolate milk. It's just right in the middle!
So there you have it! Vanilla milk is just milk with a yummy vanilla taste added to it. Yum!