Before diving in much deeper, we should stop for a moment and define intelligence. Intelligence is simply the ability to learn something then apply that knowledge. Artificial intelligence, at least for our purposes, is the illusion of intelligence. Our intelligent entities need not necessarily learn things, but must at the very least convince the player that they are learning things. I must stress that these definitions fit game AI specifically. As we'll discover later in this section, there are many applications for AI outside of games, where other definitions are more adequate. 

Intelligent creatures, such as humans and other animals, learn from their environment. Whether it's through observing something visually, hearing it, feeling it, and so on, our brains convert those stimuli into information that we process and learn from. Similarly, our computer-created AI must observe and react to its environment to appear smart. While we use our eyes, ears, and other means to perceive, our game's AI entities have a different set of sensors at their disposal. Rather than using big, complex brains like ours, our code will simulate the processing of that data and the behaviors that model a logical and believable reaction to that data.

AI and its many related studies are dense and varied, but it is important to understand the basics of AI being used in different domains before digging deeper into the subject. AI is just a general term; its various implementations and applications are different for different needs and for solving different sets of problems.

Before we move onto game-specific techniques, let's take a look at the following research areas in AI applications that have advanced tremendously over the last several decades. Things that used to be considered science fiction are quickly becoming science fact, such as autonomous robots and self-driving cars. You need not look very far to find great examples of advances in AI—your smartphone most likely has a digital assistant feature that relies on some new AI-related technology. It probably knows your schedule better than you do! Here are some of the research fields driving AI: