Well kiddo, a river goddess is like the boss of a river. Just like how a teacher is in charge of a classroom, a river goddess takes care of the river and makes sure everything is running smoothly.
In some cultures, people believe that rivers are very important because they provide water for drinking, washing and farming. So, they think it's important to have a special god or goddess who looks after the river to keep it clean and healthy.
People might pray to the river goddess if they need help with something related to the river, like if there's a drought and they need more water for their crops. They might also offer gifts to please the goddess and show that they appreciate all she does for them.
Overall, a river goddess is like a powerful and important figure who takes care of one of Earth's most important resources - water!