As mentioned, ‘The King’ engine has been around for over 20 years and it keeps on improving as computing power increases.
The game features a database of ‘personalities’ according to rank, some just mere beginners, some on the way to grand-mastership; these 'virtual-chessers' also have a personality, some liking to attack early on whilst others being more conservative. That’s not all however, as players have specific traits, such as moving the queen early or favouring king safety. To top if off, you have famous masters in the database too, which makes it a great feature particularly for players who want to gradually improve at the game.
You also have the possibility of entering the ‘Academy’, and going through the tutorials available. There is a standard tutorial with the game and two tutorials by grand-masters Larry Christiansen and Joshua Waitzkin, complete with audio. The Waitzkin tutorial is more centered around attack but they are both highly recommended; aside from basic 'forks' and 'skewers' you will also learn a lot about the pressures of playing for a rank.
Apart from tutorials or ranked games you can look at famous games of the past in the database, or refresh your memory on widely used openings.