What kind of applications (software technologies) we can test efficiently using mercury QTP (quick test professional) ?

QTP stands for quick test professional which is a mercury’s product for automation testing (functional & regression testing) of below technologies.

Windows applications,
People soft
Java
SAP
ERP
Oracle
Siebel
VB
Dot net
ASP
Java script
And some Others…

Note: you need add-ins for using QTP on different technologies.
For example to work on ERP(SAP, people soft etc..) applications you need SAP add-ins, people soft add-ins etc…

What do know by ADD-ins in QTP? Properties of Test object? Runtime object?

Test objects are the one that will be recognized by QTP, where as Runtime objects are the actual objects that the test objects will be linked to.

SetTOProperty() function is used to change the properties of a test object.
Similarly GetROProperty(outer text) is used to get the outer text of object. Or you can use,
Webelement().object.outerText = “asasasasssa”.