Firstly we have to know Software Application Life Cycle, in this there are 3 phases –
1) Development phase-
In this phase developers find any mistake, they called it as mistake.
2) Testing phase-
In this phase if testers find any mistake, they called it as bug or defect or error of fault.
3) Production phase-
In this phase if end user find any mistake, they called it as failure.
Defect Management: