The basic idea of this game is to build a zoo. You can purchase animals, shops, food stands, kiosks, decorations, and expansions to improve the status your zoo. There is a social aspect to this game as well. You can visit other user's zoos and leave them a tip. This increases your heart reputation status.
Adding animals to your zoo rewards you with both money and experience. The shops reward you with experience only. Please see the animals and shops pages for more detailed information. As you gain experience points, you will move up through the levels of the game. When you make it to a new level you will unlock new animals and earn zoo bucks.