I want to know what is the difference between aerobics, cardio, and strenth training exercises?

Good question: Aerobics/cardio mean the same thing:doing activity that raises the heart rate & keeps it there. Most adults need 30 min minimum & ideally 60 min of cardio 5-7 days a wk. Strength training or 'lifting weights' has a goal of building lean muscle tissue. Do it 3 days/wk. Muscle burns calories. Without enough muscle, you can eat little and still gain weight. Also lifting weights makes strong bones.