A dataset is a collection of examples used to develop and assess a machine learning model. A practical workflow separates it into training, validation, and test data: train on the first, tune configuration against the second, and use the third once for an estimate on unseen, production-like data. section 5.2.1
The split protects evaluation from information leaks. Repeatedly changing layers or other hyperparameters after checking validation performance gradually overfits the validation set, so final evaluation requires a different dataset that has not influenced development. section 5.2.1























