WHAT ARE BUGS. Bug Bug can be defined as: ►Errors that are identified or uncovered during testing. Bugs are also called Errors, Defects, Faults, Mistakes. Reasons of Bugs/Logics of Bugs/Conditios of Bugs/ Formal definitions of bugs. ♦The software does not do something that the product specification says it should do. ♦The software does something that the product specification says it should not do. ♦The software does something that the product specification does not mention. ♦The software does not do something that the product specification does not mention, but should do. ♦The software is difficult to understand.