sklearn.cross_validation

The `sklearn.cross_validation` module is a deprecated module in Scikit-learn version 0.20. It was used earlier for cross-validation methods, but now it has been moved to the `sklearn.model_selection` module.

The `cross_validation` module provides tools for splitting datasets into training and testing sets, and for evaluating the performance of a machine learning model using cross-validation techniques. It includes functions such as `train_test_split`, `KFold`, `StratifiedKFold`, and `cross_val_score`.

`train_test_split` function is used to split the dataset into training and testing sets. `KFold` and `StratifiedKFold` are used to create cross-validation folds for training and testing the machine learning model. `cross_val_score` function is used to evaluate the performance of a machine learning model using cross-validation.

The `cross_validation` module is still available in Scikit-learn, but it is recommended to use the `model_selection` module instead.