IoT is just a network of things. So, it is about the connectivity of cyber-physical systems. Machine Learning is today more toward Pattern recognition using probability and statistical patterns of data. AI can be considered as a super-set of both technologies that can even include Expert systems and other inference engines along with Machine Learning.
If you are interested in IoT, I recommend this IoT Course by Intellipaat.
Also, watch this video on IoT, ML, and AI: