When you click start an image of a cat will show up with empty spaces for the letters of the word. Like this for example:

No letters will be revealed even if you guessed a letter correctly. You have to guess the cat breed based on the image. When you make a wrong guess you will be given a hint but be careful, you only have a limited amount of tries before you lose.
If you guess the cat breed, the word and image will change and the game will continue. This goes on until you lose or until you decide to give up.
When you finish a game, you will be shown how many cat breeds you have guessed and what is your highscore.