What's Up is another example of the minimalist game design style that has been flooding the market since the success of Love Letter, but the gameplay relates more to ye olde Memory game, with players needing to reveal things in order to collect stuff. Here's the revised, far more useful description, followed by a video overview in case you want to see the game in action:
To set up, shuffle the thirty double-sided cards, then lay them out on the table in a grid. Each card features 1-3 birds in one of four colors — red, green, yellow, purple — with the reverse of the card having either the same number of birds in a different color or the same color of birds in a different number. Thus, each number+color combination appears five times in the deck.
On a turn, choose a card in the grid, then flip it over. If you can add it to your collection, do so; if not, return the bird to the grid with the newly revealed side face up. Your goal is to collect sets of birds in a single color, with you needing to take the single bird first, then the pair, then the triplet. The first player to collect 2-4 sets wins, with the number being dependent on the number of players. Watch what others do, remember what was flipped where, and play the odds when deciding to flip the birds!