Artificial intelligence can be interpreted as adding human intelligence in machine. Artificial intelligence is not a system but a discipline that focuses on making machine smart enough to tackle the problem like human brain does.
Machine Learning is the subset of AI. That is, all machine learning counts as AI, but not all AI counts as machine learning. Machine learning refers to the system that can learn by themselves. Machine learning is the study of computer algorithms that comprises of algorithms and statistical models which allow computer programs to automatically improve through experience.