According to these, the aim of the game is simply to rear your own Baby Panda or Giant Panda (you can tickle and play with them via the touchscreen, as you would a Nintendog), keeping them fed, clean, and happy during their time in Panda Park (which, incidentally, changes depending on whether you play at day or night).
To do this, you'll get a daily allowance which can be used for panda food or toys (such as ... gherkin-shaped see-saws?), and as you play more, further Baby Pandas will gradually begin to "move" into Panda Park, which is probably just Namco Bandai's way of avoiding the whole panda sex thing. Probably for the best.
Gallery: National Geographic Panda
[Via press release]