The game works like this:
First of all you choose which spy organisation you would like to join - I choose MI6 naturally. You then carry out tasks and earn money and gain experience. As you gain more experience, more challenging tasks (with higher rewards) are unlocked.
You can buy items such as guns from the Blackmarket and finally carry out assassinations. you can even open a Swiss Bank account.
I am not sure but I think this is the first Twitter based game and if you are on Twitter, you might think twice before signing up. I am warning you - it is really addictive.