Interval basically just means "for a time". The duration and intensity of the interval depends on what energy system you are trying to target, as well as the recovery period. 5 minutes is a typical recovery period unless you are specifically trying to simulate a non-recovered state. For example, Tabatas, various on/off durations, etc. all have very short rest periods. 1 minute is a common anaerobic interval, 3-5 minutes is a typical VO2-max interval, and 20 minutes for threshold, and commonly all recommended to be done with 5 minutes of rest between them.