The extension for Script file is .mts
and the extention of the repository file is .tsr

Extension for test script:->
* The extension of Test Script File : .mts

Extension for test repository:->
* The extension of test repository(per test): .tsr
* The extension of tesr repository(shared): .mtr

Hi poonam can you check whether tsr is for shared and mtr 
is for per test??

OR both mtr and tsr can be shared across???   ;)

The extension for :

                  SCRIPT file :   .mts
         
                  OBJECT REPOSITORY (shared)     : .tsr

                  OBJECT REPOSITORY (per action) : .mtr

Can anybody tell what are the extension of the below:

.tsp
.tsr
.mtr
.mts
.bdb

This is the first time posting the answer. there are 6 
extns are there in QTP.

Batch test:.mtb(Mercury test batch)
Peraction Repository: .mtr(mercury test repository)
Shared repository:  .tsr(test shared repository)
script: .mts(mercury test script)
functions : .vbs
Recovery scenario :.qrs(Quick Recovery scenario)