When you boil down a liquid or food, or when it boils down, it is boiled until there is less of it because some of the water in it has changed into steam or vapour. He boils down red wine and uses what's left = reduce
be cooked until very little liquid is left; "The sauce should reduce to one cup"
If you say that a situation or problem boils down to a particular thing or can be boiled down to a particular thing, you mean that this is the most important or the most basic aspect of it. What they want boils down to just one thing. It is land = amount to