Cross Validation WEKA random

WEKA Cross Validation:

 Classifier cls = new J48();
 Evaluation eval = new Evaluation(data);
 Random rand = new Random(1);  // using seed = 1
 int folds = 10;
 eval.crossValidateModel(cls, data, folds, rand);
 System.out.println(eval.toSummaryString());

What does it mean "rand"? How does cross validation in this case? 10 folds are always mixed?

Thank you!