Need an explanation about validation data during training the model

Hello, I have a question for the training of our model.

- When we fit our model we are passing data as arguments. However, can somebody explain this to me why we passed validation data as in (validation_inputs, validation_targets) form rather than passing directly validation_data variable we have created?

- I watched the previous videos but still cannot figure out. 

- Also, I have used directly as validation_data variable. The code indeed work without problems but I may have been lucky this time. 

So this is why I appreciate a simple explanation why we set validation as inputs and targets.

Thank you

Burak