Bug

An error or flaw in software that causes it to behave unexpectedly or incorrectly. Bugs range from minor visual glitches to critical data corruption or security vulnerabilities.

Every software product has bugs. Understanding the bug lifecycle (report → triage → fix → verify) helps you manage developers, communicate with users, and prioritise fixes rationally.

A user reports that the "Save" button on her profile page does nothing. The founder logs it as a bug, assigns it priority "high" (it blocks core functionality), and it's fixed in the next sprint.