Slips are errors where users intend to perform one action but inadvertently complete a different, often similar one. For example, clicking "Reply all" in an email instead of "Reply" is a slip or accidentally selecting "Print 10 copies" when you intended to print just one.

Slips generally happen when users are not fully focused on the task, typically operating on autopilot. They frequently occur with experienced users who are very familiar with a task's processes, i.e., they understand the goal and the steps involved but occasionally take a wrong step due to a lapse in attention.

Conversely, mistakes occur when users have a misunderstanding about how to perform a task or implement it wrongly, often seen with newer users still learning a system’s functions.