Three flips is correct. The idea, which could have been explained better, is to flip the coin repeatedly until you get HT, or TH. Once you have achieved that, you take the first of those two flips (either H or T, respectively) and that's your fair flip.*
When you have a fair coin, there is still some probability that you will get HH or TT on your first two flips- on average it will take you three flips to get HT or TH- which is why is says "Average 3 Flips" when you move the slider to 50%. Try it if you don't believe me.
As someone mentioned, if you know the bias (or lack thereof) of a particular coin, you don't need to use the "flip till you get HT or TH" algorithm. But it becomes useful when the coin's bias is unknown.
When you have a fair coin, there is still some probability that you will get HH or TT on your first two flips- on average it will take you three flips to get HT or TH- which is why is says "Average 3 Flips" when you move the slider to 50%. Try it if you don't believe me.
As someone mentioned, if you know the bias (or lack thereof) of a particular coin, you don't need to use the "flip till you get HT or TH" algorithm. But it becomes useful when the coin's bias is unknown.