The term 'Big Bang Theory' refers to a popular American sitcom that aired from 2007 to 2019. It follows the lives of four socially awkward scientists and their neighbor, a waitress and aspiring actress. The show was a huge success, winning 10 Emmy Awards and becoming one of the most watched television shows in the world. The term 'NERD' is a four-letter word that is often used to describe the characters in the show, as they are all highly intelligent but lack social skills.