Mean time to recovery (MTTR) is the estimated amount of time between a failure and recovery of a device. Mean time between failures (MTBF) is the average amount of time between failures of a device (generally provided by the manufacturer). Mean time to failure (MTTF) is the length of time a device lasts in operation. MRTR is something we made up.
Mean time to recovery (MTTR) is the average time that a device will take to recover from any failure. Examples of such devices range from self-resetting fuses (where the MTTR would be very short, probably seconds), up to whole systems which have to be repaired or replaced.
The MTTR would usually be part of a maintenance contract, where the user would pay more for a system MTTR of which was 24 hours, than for one of, …