RPO and RTO are the two numbers that define a disaster-recovery target. RPO (Recovery Point Objective) is how much data you can afford to lose, measured in time — an RPO of 5 minutes means backups or replication must be at most 5 minutes behind. RTO (Recovery Time Objective) is how long you can be down — how fast you must be back up.
Worked example: a bank might demand RPO near 0 (no committed transaction lost, requiring synchronous replication) and an RTO of minutes; a blog might accept RPO of 24 hours (nightly backup) and RTO of a day. Gotcha: tighter targets cost exponentially more — near-zero RPO needs synchronous cross-region replication (latency and money) — so set RPO/RTO per dataset by business impact rather than demanding the strictest everywhere.