I read a blog post about mitral valve prolapse. but i'm still not clear - what is it?

Valve abnormality: Mitral valve prolapse is a structural abnormality of the mitral valve that causes the mitral valve to bow into the left atrium (left upper heart chamber that receives oxygenated blood back from the lungs) during valve closure. Mitral valve prolapse can be associated with valve leakage that may be progressive. In many patients, this is an incidental finding and they are asymptomatic.