Often abbreviated as HIIT or HIT, this form of training can be applied to both aerobic exercises (cardio) and weightlifting. It is proven to burn more fat than classic exercising (CE), in the same or even less time.
While HIIT is a better way to burn fat, it is much harder to do than distance running. A person that's able to run 5kms by slow or medium paced jogging in one session might not be able to run 5kms by HIIT.
The concept of HIIT is to alternate between sprinting and slow jogging/walking in ratio 1:2. I will give you an example of full exercise.
3 minute warm up - light/medium jogging
10x 30 seconds of sprinting followed by 1 minute of light jogging
3 minute cooldown - light jogging
After 5 rounds of sprinting/jogging you take a rest and walk for as long as needed - however keep it to minimum.