This lecture introduces the CEPA, a group of enthusiastic but unsuccessful extraterrestrials who send a duo to Earth to learn how humans understand the world. Through the story, the lecture explains the invention of compilers by Grace Hopper, which translate human language into machine code, making it easier to find and fix errors. It also covers the origin of the term 'bug' in computing, referring to a small insect found inside a malfunctioning computer.