When a database restore is done, it overwrites your existing database with a copy which was on your backup.  If you accidentially do a restore instead of a backup, this means you will be over-writing your real database with an older one, which you dont want.

However when a database restore is done behind the scenes it takes a copy of the old database before it gets overwritten.  This file can therefore be used to undo a restore if required. 

For those technically savvy enough, the old file is called property.old and the new database is called property.mdb.  Deleting the property.mdb file and renaming the property.old file to be property.mdb does the undo operation.