Okay kiddo, an accumulator is like a big battery.
You know how your toy robots or cars use batteries to work? And when the batteries run out of power, the toy stops moving? In the same way, the energy accumulator stores energy, so we can use it later when we need it.
For example, if you have a toy car that needs to move for a long time, we put a bigger battery or many batteries to make it work longer. And that is how an accumulator works too! We use accumulators to store energy for a longer period and use it when we need it. It is like putting more and more batteries together to make a bigger battery.
Also, people use accumulators to store energy from the sun and wind. Sun and wind produce energy that we can collect, but sometimes the sun doesn’t shine or wind doesn’t blow. So, to make sure we have energy when we need it, we store it in an accumulator!
That's all, little buddy. Did you understand it?