Super soldiers are, literally, soldiers who are super. Whether it is because of genetic enhancements, cybernetic implants, surgical procedures, or perhaps just because of the equipment they wear, they have been artificially rendered much more than they were originally, and are more powerful, stronger, tougher, smarter, deadlier as a result. They are usually given the biggest and best toys as so should not be messed with under any circumstances.
Super soldiers do not include soldiers gifted with supernatural abilities (ie. superheroes), but soldiers who have been artificially enhanced to be as good as they are.
They also do not include soldiers who are naturally talented (ie. Samus Aran) or action hereos (Vin Diesel, John McClane).