Why Debugging?

once creation of script(s) got completed, to ensure the script is free of errors one has to perform debugging.

Purpose of Debugging:
1. To Find syntax errors.
2. To Add Breakpoints.
3. To Execute single line of step(s).

QTP will check your script for syntax errors whenever you switch from the Expert view to Keyword View. The SYNTAX Error window displays the following information for each error in the script.
Break Points allow user to suspend a run session at a pre-determined place in the script in order to inspect the run time state of application.
The step commands in the DEBUG menu allow user to execute a single step of a script, these commands are available once a run session has paused.