Food Science/Food prep
Of courses it doesn't mean we should save ourself from the flavor enhancing powers of marinades. Basically what it does it that softens the texture of the meat or vegetables you are marinating and usually add infused flavors into the food.
In this case, sos means:
Seasoning Oil-Something that is oil/fat Spice-Things like salt and pepper
The things about marinades, unlike brines, is that typically the flavor is concentrated on the surface of the food source.
It works on the principles of how acids denature or breakdown proteins, resulting in a more tender texture.
Though the science of brining is not fully understood, it works on the concept of osmosis and since it has more salt on the inside of it, it is more likely to hold moisture in during frying, baking, and grilling. Basically it is a salt/Water mixture in which other spices can be added to add flavor.