Energy is what makes everything happen. Imagine a toy car that moves when you wind it up - the energy stored in the car's spring makes it move. But energy can also come from things like heat, light, or even the food we eat.
Now, an energy being is a type of creature that is made entirely out of energy. They don't have a physical body like you and I do, but instead they are like a ball of light that can move around and do things.
Think of it like a firefly - it glows and flies around, but it's not made of the same stuff as the tree it's sitting on. In the same way, an energy being is made of a different type of energy than the things around it.
Some people believe in energy beings, like ghosts or spirits, because they think that when a person dies their energy is released and can take on a new form. Whether or not you believe this is up to you, but it's a way that some people try to explain the mysterious things that happen in the world around us.