Edward is a "vegetarian" vampire while James is a "regular" vampire. Edward can see people's thoughts while James is a tracker. The way that you could tell physically which is which, Edward's eyes are golden "liquid topaz" as Bella describes them, while James' are crimson. But both turn black when thirsty. Victoria keeps saying Edward killed James while this is not true. Emmett, and Jasper, (and Alice in the film) kill James. Edward is Bella's lover, James almost killed her.