.vbs in QTP
.vbs stands for VB Script.
It is a file extension of VB Script. You can write the VB script in this file and can associate it to your QTP Test file. Or you can use ExecuteFile Statement in QTP Test file. It is same as .qfl file.
Only disadvantage is, you can not put breakpoint for debugging purpose in this file where .qfl file provides this facility. Always prefer .qfl to write VB script than .vbs in qtp.