The typical Heart Valve has 3 (Tri) Leaflets to the Valve. Bicuspid, has 2 (Bi) Leaflets to the Valve. The Leaflets flap open and closed with the pulsing for the heart. The Heart is a Pump. When it contracts, it forces blood to move thru the body. The Valves keep the blood from rushing backwards into the Heart in the case of an Aortic Valve. One in a 100 people have the condition of Bicuspid Aortic Heart Valve, so just 1% of the population which seems small, but that a lot of people when your population is 300 million. Still an exclusive club!
The Bicuspid Valve having just 2 Leaflets wears out much sooner than the Tricuspid Valve. The two leaflets become calcified and stiff and will fail to open and close all the way. They call this Aortic Stenosis. I had all this. Lost energy, couldn't hike on the trails. Had the Valve replaced with a Man Made On-X valve and all is better for the rest of my life.
Hope this helps!
All the best to you!