Being an endless running game, you can never actually 'win'. The objective is more to score as highly as possible, place far up the leaderboards, and accumulate Coins which can be used to help you score more next time, and achieve various goals.
Compared to the original Temple Run, you will notice a few differences. First, the game is set in a city in the clouds, rather than the land-based temple of the first Temple Run. There is also a new mine cart section to enjoy, and much-improved graphics. The actual gameplay itself is pretty much identical. You lean your runner by tilting the device, allowing you to go dodge most obstacles. Perform a horizontal swipe action on the screen to take a turn in the road, with a vertical one allowing you to jump or slide over or under obstacles.
Should you fall down a gap, not turn correctly, or be caught by the pursuing ape, you will lose. The game gives you a chance, at this point, to continue in your run, if you are willing to pay real money for it, but otherwise you are forced to start again and begin a new run.
Temple Run 2 is somewhat old-fashioned in that it is largely focused around getting as high a score as possible, surviving as long as possible. You can see your current score in the top right-hand corner, which increases both through the amount of time you have remained alive, and the number of Coins that you have collected.
As with most games nowadays, you are able to advance through the game's levels to unlock certain bonuses. These include things like Coins and Gems to purchase new abilities and unlock new characters.
These affect aspects of your character's play, such as the length that the Shield will last, or how many Coins you have available to collect.