It's a roleplaying game (although probably not the kind you're used to.) You go along with the story and your list of abilities/skills/attacks designated on your character sheet.
ik what dnd is. just not details, like what races and classes and stuff that are available. but I guess that would depend on what the dm wanted to use or something
are you guys gonna be using text or voice chat?
Roll20.. There are also other programs that make an interactive table. So Skype plus one of those.