“Existence precedes essence” means that we as human beings existence before we actually define who we are as human beings. When we are first born, we don’t know what we are going to be when we grow up. We don’t know what lies in the future. It is not until we figure out our purpose for ourselves that we create who we truly are. For example, say you have a chair that has three legs and a broken back. We know that the details of this item make a chair, but until then this chair is not defined for a purpose. It is not until we fix the broken back and add a leg that a person can actually sit in the chair. Then we know that the define purpose for this chair was for people to sit in it. This is the same concept that Sartre is trying to get us to understand when he says existence precedes essence.