Understanding the rdiff-backup restore syntax

[Eric Beversluis via Any discussion of rdiff-backup]

I'm trying to learn my way around restoring from rdiff-backup. I'm 
looking at
https://rdiff-backup.net/rdiff-backup.1.html#_restoring
I see this sample:

rdiff-backup restore --increment \
    /backup/rdiff-backup-data/increments/usr/local.{time}.dir \
    /usr/local.old

What do the back slashes indicate--why are they there?


--
Eric Beversluis
www.ericbeversluis.com
2x Honorable Mention--Writer's Digest Contest