ERROR, BUG and DEFECT
Bug: A fault in a program which causes the program to perform in an unintended or unanticipated manner. Or Deviation from the expected result. A QA team or software tester can find the bug. Famous bug- millennium bug. (data Problem) i,e, Y2K Bug
Defect: Mismatch between the requirements. From user point of view it effects the business directly. E.g instantly halt in the system.
Glitch: A minor malfunction, mishap, or technical problem on computer system known as Glitch.