For the purposes of weight and balance and expressing wing loading values, weight and mass are the same thing and the terms are used interchangeably (you will see "Weight and Balance" and "Mass and Balance" used in documentation).
So wing loading refers to the ratio of the area of the wings relative to the total mass or weight. Wing loading is normally expressed, in North America, in lb/sqf, and in metric jurisdictions, in N or Kg/sqm.
As you go faster, the wing is able to support a given mass/weight with less and less total area, and it's more efficient overall, if your priority is to go fast, to reduce the wing area, while keeping weight/mass the same, to take advantage of that. This is because the airfoil's most efficient AOA (max L/D) is at a fairly high angle and from a speed-efficiency perspective, you want to cruise as close to that AOA as possible to minimize induced drag.
The side effect of this is still higher minimum flying speeds than otherwise, but if your priority was to go fast, you live with that. Wing flaps allow you to cheat your way, at least partly, out of this problem, by making your small wing work a lot harder at low speed than it would without flaps, then you can retract them so they are out of the picture when you want to go fast.
It's not that different really from water skiing on a small ski vs a big ski. You can go faster on the "high ski loading" small ski, but it has to go faster to get on the step.
The small ski will also ride wavelets a lot better. Same with wings; one benefit of small highly loaded wings is a better ride in bumps and you need that characteristic, since you are going faster, if you want to do it comfortably.
You see this effect clearly with light aircraft. The Thorp T-18 gets by on only 86 sqft of wing area at a gross of 1600 lbs, to cruise at 180 mph. The Pazmany PL-2 has more or less the same overall configuration and all up weight, but has 116 sqf of wing area, a significantly lower wing loading, and cruises about 25-30 mph slower on the same power and most of that is due to the larger wings and lower wing loading.
The Thorp also lands and takes off about 10 mph faster, which is bad, but it also rides bumpy air way better, which is good (I own a PL-2 and have flown in a Thorp in the past).
The aviation gods giveth, and they taketh away...