Answer Description

Recovery Time Objective (RTO) is a predetermined amount of time a business solution or process can remain offline following a disaster or incident. It will be different for each business and process but it essentially says "this is how long our business can survive without process or system XYZ." For example a warehousing system for a retail store may have an RTO of 24 hours, because stores can continue selling existing inventory but will likely run out in about a day without new shipments from the warehouse.

Real Time Actual (RTA) is sometimes used for tracking actual recovery times during rehearsals or incidents. MTTR and MTTD are Mean Time to Detect/Recover and are specifically used for cyber security incidents. They are metrics for tracking the time it takes to detect a threat, and recover or remove the threat.

Wikipedia

Disaster recovery is the process of maintaining or reestablishing vital infrastructure and systems following a natural or human-induced disaster, such as a storm or battle. It employs policies, tools, and procedures. Disaster recovery focuses on the information technology (IT) or technology systems supporting critical business functions as opposed to business continuity. This involves keeping all essential aspects of a business functioning despite significant disruptive events; it can therefore be considered a subset of business continuity. Disaster recovery assumes that the primary site is not immediately recoverable and restores data and services to a secondary site.