You have in this mod available Singleplayer with storyline. There you are on your own and can see how evolved vanilla freelancer story. You can in SP use only one ship/time. In MP you have to dealt with other players as also npcs, there is not written storyline, you with your actions do your own story. In MP you can have 5 characters per account and you can have unlimited amount of accounts. For details is good to look into Crossfire wiki.