VRDB is how avast stores the necessary info to restore executables (*.exe, *.com) files.
VRDB is not a backup system, the stored information is very small (not the whole files).
Besides, only Win32 executables are processed.
So it's not a backup utility, but a restore feature of avast.
What avast can clean it does very well, i.e., it really cleans.
avast is not as good on cleaning as other antispywares (like SuperAntispyware, for instance).