Is Artificial intelligence simply taking decisions on the basis of values produced by a machine learning model
Artificial Intelligence is a very broad area of Computer Science which is intertwined with many other fields, and someone might argue that its definition is the discipline that develops rationally acting systems.

When it comes to Machine Learning, the generally accepted definition is programming computers to perform a specific task without specific instructions about the problem.

Being that broad of a field, AI comprises Machine Learning problems, but the difference between the two areas relies on how you devise your system:


if you make use of problem-specific knowledge in your algorithm: you're outside the ML field;
if you formulate your problem in a general-enough manner and use a generic algorithm: most likely you're inside the ML field.


I'm sure you have already seen this image from Nvidia a million times already, but it's intuitive to understand what's the relationship between AI and ML: the latter is part of the former.