Bug Report
A bug report is the documented record of a defect — a clear title, steps to reproduce, expected versus actual results, environment details, and supporting evidence — written so someone who wasn't present when the bug was found can understand, reproduce, and eventually fix it.
The single biggest determinant of a bug report's usefulness is reproducibility — a report that says "checkout is broken" is nearly worthless compared to one with numbered steps, the exact browser and OS, the specific input used, and a screenshot or video showing the actual failure state.
Good bug reports also separate observation from interpretation: "clicking Submit shows a blank page" is a fact the reporter directly observed; "the API must be timing out" is a guess that might send an investigation in the wrong direction if it turns out to be wrong — the strongest reports report facts and clearly label any speculation as speculation.
