When you test your applications, you may want to check how the application performs the same operations with multiple sets of data. For example,suppose you want to check how your Web site responds to ten separate sets of data. You could record ten separate tests, each with its own set of data. Alternatively, you can create Data Table parameters so that your test runs ten times, each time using a different set of data.this way of setting parameters is called parameterization.
If you want to enter the values in the DataTable in QTP then we go for parameterization.You see the below navigation (tools->datadriver->parameterized) especially in the concept of 'recovery'(single window ,multiple window handling ) Source: CoolInterview.com
In QTP, the single script used to run the multiple sets data and perform the same operation by using data table... For example, ->Open microsoft address book. ->Click record button in QTP, ->in address book click New->New Contact, ->add first name "dinesh" and last name "kumar", and click ok. ->click STOP in QTP, ->Go to Expert view in the QTP Screen, ->In that screen expand all the items which is recorded in QTP. ->In Value column just click on the First Name, you can see one button "<#>" like this. otherwise press "Ctrl+F11". ->you will get one new window called Value Configuration Options. ->in that window you can see 2 radio buttons. ->Select the 2nd one,naming Parameter. ->in that combo box select Data table. ->Then set the Name field as FNAME, ->Select the first one, Global sheet. ->Just click ok. ->Do the Same thing for last Name edit box. ->Finally you get one Data table in the bottom of the QTP Window. ->In that Data table you can add multiple data's as many as possible. ->If suppose you didn't get any Data table means goto click View menu in the toolbar and select the data table. -> now run your script. ->The data's are succesfully added in the address book which are stored in the data table.
(Note: you should change the Property value in object repository. Removing the innertext of the property window,the QTP easily recognize the object.) Source: CoolInterview.com