It's a UN initiative to let people play vocabulary based quiz and for every correct answer 10 grains of rice are donated. Donations go to UN World Food Program .
It also informs that approximately 3.8 billion grains have been donated since its launch on 07-Oct. I donated too and would suggest others to spend 5 minutes out of a few hours of monitoring cricket scores on the net or while chatting with your friends.
Deviating a little from the main topic and looking at the two aspects of the
website.
Vocabulary:
I don't think such a quick quiz can improve one's vocabulary substantially. It
takes time for an individual to assimilate new words and such time does not exist in this case. But, it could still be used as a refreshment from busy schedule or to gauge your vocabulary levels. If you try taking away just 2 words a day then some lingual gains could be made as well.
Donation:
UN being the most respected organization when it comes to world development, I cannot challenge the effectiveness of this initiative. But, I have doubts about how much rice registered on the servers actually translates to real rice? And then we all know about the rest of the delivery chain and how much will reach the end! Going by the 3.8 billion figure, it translates into approximately 3,80,000 KG of rice, assuming 10 grains would weigh 1 gram. Per capita consumption of rice in Indian urban areas is around 4.7 Kg per month. Considering higher consumption in other countries, in less than 3 months this program should have donated rice to feed 70 to 80 thousand people for 1 month. I doubt so many people would have been freed from hunger. But it is worth spending a few minutes every day for a fraction of that.