FITT Principle - Definition

Frequency - How often you carry out physical activities.

Intensity - How hard you exercise.

Time - Duration of each exercise.

Type - A specific type of activity to target a goal.

Example:

Frequency - I exercise thrice a week.

Intensity - I go through tough training every time and noticed that my rate of heart beat is getting higher and increases every time I increase my speed or amount of strength used. 

Time - I spend at least 1 hour exercising each time.

Type - I jog and sprint on the treadmill and also swim and do rigorous sit ups.