What is actually the best exercise

No exercise alone will help you in losing fat. You will have to eat a balanced diet also. Some of the exercises you can do especially for belly are situps or crunches and squats.

Squats and Lunges are the best.

Madhu Gupta,
Best is EXERCISE....rather than best exercise...!!!!

Skipping is a very effective exercise as I have personally felt noticeable changes after I have started skipping...

Also some bending exercises such as to touch your toes with your fingers keeping your legs stretched is also a very effective exercise

one of my old friend suggested me doing prayanam,pulling abdominal muscles in for few minutes everyday and gradually increase the reps.

Exercise increases circulation, tones up the muscles, reduces stress levels, and slows the aging process, fights toxins increases energy and so much more.
I think laughter is the best exercise then any.

If you have only 30 minutes a day - RUN.
Running is the best exercise. Going back to anthropology, human beings were designed to hunt and gather. Hence, if you want to look and feel like a hunter - Run. Go gradual, slowly increase how much you run - but if you want to lose weight - there is nothing better than running.
Also - remember the 50-30-20 rule - 50 % of what your weight is depends on your diet. 30% on your cardio and 20% on your muscle training.

@Yossarian,
very well said....yes it makes sense....!!!

@Yossarian I liked the 50-30-20 rule! Well said.

I personally prefer running too!

I personally do swimming and running to maintain my health and body shape.
I also drink lots of water to maintain ph balance and its one more advantage is intake of more water help you to loss weight or for maintaining weight.

I understand that deadlifts, squats, bench press, and pull ups are an
awesome foursome. This 57 yrs old guy has tried it for the last 8 months
and i feel 37 again! (Footnote)... Nutrition is also a MUST. Stay hydrated!