 So water is one of the most common substances in our galaxy. The vast amount of water that's in our galaxy is actually permanently frozen because the temperature is well below zero Celsius. Now Earth, as it happens, exists in a Goldilocks zone where the temperatures that are a result of the heat that's provided by our nearest star, which is the Sun, are not too hot and they're not too cold. They're just right for water to be at its liquid phase, which is a requirement for human life. The molecular structure of water is such that for each molecule of water there's two hydrogen atoms and one oxygen atom. Now the hydrogen atoms are associated with the positive electrostatic charge, the oxygen with a negative electrostatic charge, so that when you've got lots of molecules that are interacting with one another, they interact in such a way that the positive atoms, the positive parts of the molecule and the negatively charged parts of the molecule tend to attract just like magnet. Now this attraction is what's called a hydrogen bond and it's an extremely strong electrostatic bond and it's one of the many quirks of water.