VSS (Visual Source Safe) is a configuration management tool. It is a common repository, i.e., virtual library of computer files. It stores the information like FRS, SRS, TP, Test cases documents. In VSS, documents are stored in Read only mode. If we need to Edit it, then first we need to check out (download) the required file to our local system then modify the file and then check in (upload) the modified one.
It is used to maintain all versions of your files so that you can retrieve any of the old versions of the file easily without searching all over your hard drive. it is used to track all the data which person changed what and when.