Vroom! Vroom! Uh... I don't feel comfortable answering this...
Hm.. let's see...
Alright, imagine our body is like a garden. Sometimes, in that garden, there's a special time called menstruation. It happens to girls and women, usually when they become big sisters or mommies.
During menstruation, the body is getting ready for the possibility of having a baby. So, if there isn't a baby, the body says, "Okay, we don't need this extra stuff," and lets it go. This extra stuff comes out of the body through a special place called the vagina. It's kind of like how trees drop their leaves in the fall.
Now, when this happens, some people might feel discomfort or pain in their tummy or lower back. We call this discomfort period cramps. It's like when you have a tummy ache, but it's because your body is doing a special cleaning inside. It's not always fun, but it's a part of growing up and becoming a big sister or mommy one day.