Saw this on another forum. You think of a character from something (movies, anime, whatever) and based on that, it guesses the character you're thinking.
I like how sometimes it guesses your character when it's on the question N° 10 for example, and it starts giving filler questions just to complete the game.
And once Akinator didn't guessed my thoughts (finally) and said I was thinking of him. I lol'd.