2 of 2 Terminology corrected

What is use-value according to Marx and why is it what is valuable in a commodity?

According to Marx, labor is what gives a commodity its value, specifically useful labor(das mudpie). My question here is what exactly is useful labor and why is labor itself what provides value and not the usefulness? Is it not a contradiction to say labor is what provides value when the usefulness is what is necessary for labor to have any value in the first place?