What is Autorun.inf on External Hard Drive?

Hello,

I recently purchased a new Macbook and formatted a new LaCie Rugged external hard drive with the computer. I then set up a time machine backup to use this external hard drive. After Time Machine finished backing up my computer, I opened the drive and saw two items. One was backups.backupdb which contained the backup and the other was a file titled autorun.inf. I googled this file and almost every result said it was a virus. Is it in fact a virus? Is this file supposed to be on my external hard drive after setting it up for the first time and performing a time machine backup?