Textbook on deep learning (MIT press): https://www.deeplearningbook.org/
Online, easy-to-read articles about machine learning and data science. A good place to look for a concept for the first time: https://towardsdatascience.com
An easy guide to ALL reinforcement learning algorithms: https://stable-baselines.readthedocs.io/en/master/
Educational resource for deep reinforcement learning: https://spinningup.openai.com/en/latest/