Bug can be defined as the abnormal behavior of the software. No software exists without a bug. The elimination of bugs from the software depends upon the efficiency of testing done on the software. A bug is a specific concern about the quality of the Application under Test (AUT).

Bug Life Cycle

In software development process, the bug has a life cycle. The bug should go through the life cycle to be closed. A specific life cycle ensures that the process is standardized. The bug attains different states in the life cycle. The life cycle of the bug can be shown diagrammatically as follows:

 
The different states of a bug can be summarized as follows:

1.       New

2.       Open

3.       Assign

4.       Test

5.       Verified

6.       Deferred

7.       Reopened

8.       Duplicate

9.       Rejected

10.   Closed 

 Read in Detail here : http://www.mindstick.com/Articles/6325230e-b560-4500-8d56-d0c4d6c98c5e/?Bug%20life%20cycle