Life variable is used to determine the properties of elements that need an extra number to remember what they are. For example, metal being sparked uses the Life numbers 1 through 4 to ensure that sparks don't easily loop over themselves, and to make logic possible.

...While Water on the other hand, starts at like 30 and goes down, preventing sparks from passing through it for much longer than normal metal.

This life view is for viewing these, so that when something is behaving unexpectedly, we don't have to hover the mouse over every particle to see which particles are changing Life inappropriately.