A "computer bug" refers to an error or flaw in a computer program or system that causes it to produce incorrect or unexpected results. Bugs can arise from mistakes in coding, design, or even hardware malfunctions. They can lead to software crashes, data loss, or security vulnerabilities, affecting the overall performance of a computer or application. The term "bug" originated in the 1940s when a moth was found causing issues in a computer at Harvard University. Since then, it has become a common term in the field of software development and computer science, highlighting the importance of debugging to ensure software reliability and functionality.