The way that the site works is that the creators clock and calculate the amount of water generated or "donated" by the user, and give World Vision the equivalent monetary value of the water, the revenue for which is generated via the advertisements on the site. World Vision then supply developing nations with clean drinking matching the number of liters that helpthirst.com has produced.
The website features a mathematical "memory" game. A number is displayed in a rather cute droplet shaped area on the screen, alongside an ever decreasing blue bar, so you only have a certain amount of time to memorize this number. Once the blue bar diminishes entirely and the time is up, you have to enter the same number, either through the web-based pad provided or through your own keypad. For every correct answer, you have donated a cup of water. The numbers get more complicated and longer as the levels progress. The interesting thing is, these are not just actual numbers - they are actually numbers to the populations of different countries, the area of a certain place/country, the GDP of a certain place, etc. A little question (for example: What is the GDP of the United States? Answer: 13843825 million USD - u better memorize that!)
According to the creators the game helps improve your short term memory recall, and falls under the category of something called "Daily brain training" or "Daily brain conditioning". It is supposed to be helpful in improving memory, attention, focus and the ability to calculate mathematical figures quicker, thus improving cognitive function.
The HelpThirst people calculate 1 cup at 100 ml, and a liter = 1000 ml, which results in 1 liter of water for every 10 cups donated. That's marvelous, don't you think? Overall, I really like this website, however, the only qualm I have is about the format of the questions involved - the time allotted passes so quickly that although I may be conditioning my brain to react/memorize faster, I am not really retaining the facts, such as what the actual question was - I merely remember the numbers! But you can't have it all! It is still an extremely interesting and fun game - and I realize that I am able to memorize the numbers better the more I play! :)