score(X_train, Y_train) 이부분 이해가 ㅠㅠ

logreg = LogisticRegression()

logreg.fit(X_train, Y_train)

Y_pred = logreg.predict(X_test)

logreg.score(X_train, Y_train)

which gives: 0.80471380471380471

I use to use this method instead to determine my model accuracy:

from sklearn.metrics import classification_report

logreg = LogisticRegression()

logreg.fit(X_train, Y_train)

y_pred = logreg.predict(X_test)

print(classification_report(y_test, y_pred))

선생님 score(X_train, Y_train)이부분이 이해가 가질 않습니다ㅠㅠ 어떻게 y_test없이 train세트만으로 정확도 측정이 가능한거죠?? 혼자 알려고해도 알수가 없네요ㅠ 자세한 답변 부탁드리겠습니다!!