What is the difference between someone with 3 valves in their heart and someone with a normal heart?

See below: are you referring to tricuspid atresia? This is a cyanotic congenital heart disease where the tricuspid valve is absent (technically three valves present), these patients often times have a single ventricle and require a complex surgery to address it. Normal individuals have 4 main valves - tricuspid, mitral, pulmonic and aortic valves.