You forgot some needed information: Where is it located? What's its name? Is it at the backup location that you can set in the LR preferences? What's your OS?
It probably is the backup of the catalog. LR does not backup your images, it only creates a backup of your catalog at the intervals you set in its preferences.
Yep, catalogue (database) back-up, most like.
Delete at your own risk...
Thanks to both of you for your responses. My OS is Win7 and the file is named Lightroom. It is in the My Pictures library. Is this backup such that just the latest iteration needs to be saved or do I just need to leave it be?
LR's creates a folder Backups and in there a folder with the date and time of the backup. In this folder you'll find a copy of the catalog (*.lrcat) or in case of LR6 a zipped copy of the catalog.
You can delete the older ones a s you like - at your own risk - after making sure that these really are your old backups.
Easiest to make sure is to open LR and set its catalog options to create a backup on every close. If you now close LR it shows you the path to your backups in the backup dialog.