An Introduction to Statistical Learning: With Applications in R, Gareth James, Daniela Witten, Trevor Hastie, Rob Tibshirani, 2021 (Springer) - A widely used textbook that introduces fundamental concepts of statistical learning, including the distinction between predictors (features) and response variables (labels).
Machine Learning Crash Course: Features and Labels, Google, 2024 (Google) - An introductory module from Google's ML Crash Course, specifically defining and illustrating features and labels with practical examples.