Water fasting means only drinking water. A dry fast is no water, no food. An absolute dry fast is no water, no food, no showers. A 24 hour dry fast won't kill a healthy person - but I wouldn't advise it.
Given no knowledge beforehand, "water fast" can mean either of two things:
* You only consume water.
* You consume anything but water.
Both understandings can be inferred at face value, but only one is correct.
I too understood this as the latter before subsequent comments specified it is the former, and the name isn't even accurate since apparently consuming tea or black coffee is also acceptable.
Using as few words as possible is often the hallmark of a talented orator, but sometimes it pays off to be verbose and specific.
Water Fast means only drinking water. Standard terminology. You can verify that with a quick Google search.
1 - 2 month survival estimate is for an ordinary person. If you're obese then you can survive up to a year without food.
For an ordinary person in reasonably good health, a 24 hour water fast only provides health benefits. Up to 3 days of water fasting is beneficial. I wouldn't recommend any longer than that.
The more frequently you fast, the easier it gets. Your body adapts to burning stored fat as fuel and the hormonal hunger triggers become less severe. I've reached the stage where 24 hours is easy.