The Iris dataset is one of the classic and simple datasets. It contains the observations about the Iris plant. Each instance has four features: the sepal length, sepal width, petal length, and petal width. All the measurements are in centimeters. The dataset contains three classes for the target variable, where each class refers to a type of Iris plant: Iris Setosa, Iris Versicolour, and Iris Virginica.
You can find more information on this dataset at http://archive.ics.uci.edu/ml/datasets/Iris.
As this dataset is not present as a sample dataset in ML Studio, you need to import it to ML Studio using a reader module before building any model on it. Note that the Iris dataset present in the Saved Dataset section is the subset of the original dataset and is only present for two classes.