Ellis Island's 3 doors

From what I understood from the labels, people (including my grandfather) were assigned a place in one of 3 lines that would lead to these doors, depending on where they were going. One would lead to the US (a boat to NYC), another one would lead to more physical exams, the other one I forgot, but I don't think its the bathroom line. And to think that once upon a time my grandfather stood up there. I never met my grandfather, so visiting Ellis Island was a way of connecting with him somehow.