why do we use train test split code example

Example 1: code for test and train split

from sklearn.model_selection import train_test_split
X_train, X_test, y_train, y_test = train_test_split(
 X, y, test_size=0.33, random_state=42)

Example 2: code for test and train split

from sklearn.model_selection import train_test_split
X_train, X_test, y_train, y_test = train_test_split(X, y, 
	test_size = 0.33, random_state = 42)