Meaning: This sentence means that if a talented person is lazy, someone with less talent but who works hard can achieve more.
Choice of Words: Labor means hard work, especially physical work. Conquer means to win a fight or competition. Talent means a natural ability to do something well. Sleep means to rest with your eyes closed. When you put them together, "Labor conquers talent when talent sleeps" means that hard work and dedication can overcome natural talent if the talented person is not working hard.