Are 4k TVs Worth It?

An employee of Japanese electronics giant Sharp performs inspections on AQUOS 4K televisions in a room set at 40 degrees Celsius at the company's Tochigi Plant in Yaita, Tochigi prefecture on November 19, 2015. Kazuhiro Nogi/AFP/Getty Images

What exactly is 4k resolution? How does the number of pixels on a screen correspond to image quality? And are 4k sets really worth it?