What is Game AI ?

Notes:

Game AI:

Game AI is the branch of artificial intelligence; which deals with building
intelligent game agents i.e. game characters especially NPCs (Non Player Characters);
which act like opponents or co-players and simulate human like intelligence.

OR

Game AI is the branch of artificial intelligence; which deals with building
intelligent game world i.e. virtual world or virtual environment;
which simulates the real world
where entities of the game world behave intelligently like real world entities
and enhance player experience

Historic moment:
In the year 1997, the world chess champion Mr. Garry Kasparov was defeated by the first chess playing computer system known as Deep Blue (built by IBM).