RPO - Recovery Plan Objective - The maximum amount of time the organization is willing to sacrifice data loss after the IT outage. This can be 30 seconds, 1 hour, 3 hours, etc
RTO - Recovery Time Objective - This is an objective. It is the maximum amount of time it takes an organization to switch from production environement to the target backup environement
during an IT outage.
RTA - This is statistics - This is the amount of time an organization takes to actually switch from the production environment to target backup environment.