The explanations can vary, but the fact that an explanation is needed means that the pen is dependent. The pen requires an external set of factors to provide a reason for why it is placed in the fridge, and why it is the way that it is. For instance: the fact that the pen was made, and your son bought the pen from a stationary shop, and then put the pen in the fridge provides the external set of factors responsible for the pen. The pen is therefore dependent on these external factors, and these factors explain the pen’s existence.
