Soluble Collagen refers to the big, natural collagen molecules mostly extracted from fish or bovine skin. Spotting collagen on the ingredient list, you might think that, aha, this must be there to supplement the collagen content of our own skin, but you have to know that collagen is a huge-huge molecule that cannot absorb to the middle layer of the skin where collagen is and even if it could, it cannot just magically go the right places to become part of the skin's own collagen network. Putting collagen on your skin for anti-aging purposes is like throwing tent poles onto a ramshackle tent and expecting the tent to magically become nice and firm again.
The strong point of collagen is being a large molecule with tremendous water binding capacity, i.e. an amazing humectant and moisturizer. It produces a water-rich film on the skin giving the stratum corneum (the uppermost layer of the skin) great hydration, making it nice and smooth and reducing trans-epidermal-water loss (the process of water evaporating out of your skin).
It is also so gentle and non-irritant that it can actually be used in cleansers to reduce the irritating potential of harsh surfactants, aka cleansing agents.
If you are fine with animal-derived ingredients and know that collagen in a jar has nothing to do with wrinkles but everything to do with skin hydration, Soluble Collagen is a nice ingredient.