Please help!!! how is heart disease caused?

Everyone seems to have different ideas on this. sometimes i'm told its the build up of cholesterol, sometimes they say it is caused by inflammation and sometimes they say it is caused by foam cells. I'm really really getting frustrated because every time i come near the answer i get a different answer So please please please can someone explain to me how the clot is formed Please use complicated words if you want, i will understand them, trust me Mega thanks!!!1