The Organs of your body have their sensory touches at the bottom of your foot, if you massage these points you will find relief from aches and pains as you can see the heart is on the left foot. Typically they are shown as points and arrows to show which organ it connects to. It is indeed correct since the nerves connected to these organs terminate here. This is covered in great detail in Acupressure studies or textbooks.
Pressure Points for a Foot Massage : Press firmly on the tips of the toes to help relieve headache and sinus pain. Press firmly but do not cause pain. Hold the pressure on for several seconds at a time. Press firmly on the small rounded area just below the smallest toe - Helps with pain in the shoulder and neck area. Apply pressure on this point for up to 20 seconds.