vbs file contains the user defined functions which are
reusable that can be used in our test or compnent according
to our requirement

Hai sairam i am rajendra

         VBS means Visual basic script file

Normally QTP uses VBscript for automation script generation.
You can view this code in expert mode of QTP.

I think you are clear with this answer

if have any doubt regarding testing both manual or 
automation you can contact me

rajendra_penumalli@yahoo.com
Mobile;9885162742
Hyderabad

hi sriram 

Vbs mean Visual basic script file

open a notepad write a user defined function and save it in 
any location open->test tab ->setting->go to resource tab 
and u have option there(associtave library files) link .ur 
vbs file there and click ok

after that call that function from ur expert view.

if u are not clear ping me i will give u an example

VBS file extension is .vbs(Visual Basic Script file)

 Basically .vbs file is also called as "Library File" in QTP

A file in which the Code or functions are written in the VB 
Script format is called "Library File(.vbs)".

The functions written in library files are called 
as "Library Functions"