Chandrasekhar,
Each TestComplete project includes a collection of a tested application. You can see it under the TestedApps node in the Project Explorer (see attached imageA).
You can add applications to the collection manually in the TestedApps editor. By default, TestComplete also adds applications to the collection automatically during the test recording: it detects the application you are working with and considers it as a tested application.
The collection greatly simplifies running and terminating the applications that you test. For instance, after you added the executable to the TestedApps list, you can easily specify its command-line arguments and launch it by using the Run Test Application operation at the beginning of your keyword test (see imageB) or by calling the TestedApps.AppName.Run method at the beginning of your script test (see imageC).
For complete information on tested applications, see Managing Tested Applications in TestComplete help.