Hi Anupam,
When we found a bug while testing, We need to clarify whether it is bug or not? If u think that's a bug then we have to log the bug if u r using any bug tracking tool. If u r not using any bug tracking tool, U have to prepare the bug report in an excel sheet. Assume that u don't have any bug tracking tool.
We have to give a unique bug id to that bug. Give title of the bug then Description, Steps to reproduce, Expected Result, Actual Result, Priority, Severity, Build no., Test case id and Date, found by.
If u have bug tracking tool u'll find all these fields in that, u simply enter all these in those fields and automatically bug id will be generated.
When we log or enter a bug that should be in Active or New status. When it gets assigned to developer, he'll fix the bug and he'll change the status to fixed or resolved, After that u have to check or Verify the bug on the new build. If u didn't find any the same bug in the latest build u just close the bug. Otherwise u have to Reopen the bug. In this way bug life cycle goes on.
Cheers