Replication levels for an Azure storage account: LRS (3 copies in a single datacenter), ZRS (3 copies across availability zones in the region), GRS (LRS plus an asynchronous copy in a paired region), and GZRS (ZRS plus a copy in a paired region).
A frequent design question on AZ-305: which redundancy option lets you survive the loss of a datacenter without losing write access? ZRS. And to survive the loss of an entire region with read access to the secondary? RA-GRS or RA-GZRS.
Storage redundancy options (LRS/ZRS/GRS/GZRS) is a concept that can show up on the exam. Check the full guide to see it in context.