What is the difference between manual and automated testing?

Manual testing is performed by a human clicking, observing, and judging behavior without a script executing steps. Automated testing runs predefined checks via tools or code and reports pass/fail consistently. Manual excels at exploratory work, subjective UX, and one-off investigations; automation excels at repetition, regression, and fast feedback in CI. Automation has upfront cost (framework, maintenance, data); manual scales linearly with people and time. Most products need both: automate stable, high-value paths and keep manual effort for new risk areas. Choosing “manual vs automated” per feature is smarter than choosing one globally. Neither replaces clear requirements and good design.