Complex sentence: The tricuspid valve has three leaflets or cusps and is on the right side of the heart, between the right atrium and the right ventricle which stops the backflow of blood between the two.
Split into simpler sentences: The tricuspid valve has three leaflets or cusps and is on the right side of the heart. It is between the right atrium and the right ventricle, and stops the backflow of blood between the two.