WHAT IS IT?
Simply put, artificial intelligence is a sub-field of computer science. Its goal is to enable the development of computers that are able to do things normally done by people -- in particular, things associated with people acting intelligently. Stanford researcher John McCarthy coined the term in 1956 during what is now called The Dartmouth Conference, where the core mission of the AI field was defined. If we start with this definition, any program can be considered AI if it does something that we would normally think of as intelligent in humans. How the program does it is not the issue, just that is able to do it at all. That is, it is AI if it is smart, but it doesn’t have to be smart like us.
References on AI
Wikipedia page on Artificial Intelligence