There are different orientations of flying; horizontal -belly and back, vertical -head up and head down. And there are different styles of flying; static/formation and dynamic/freestyle.
Static/Formation skydiving is were you fly fixed positions, on your belly, head up or head down. And then you take grips with your partner(s) in different positions and combinations.
Dynamic flying is a way of flying with more movement, flying in lines which flows up and down and around in the tunnel.
In tunnel flying there’s a set order to learn because of safety. Everyone starts learning basic belly position and movements. Then you learn back flaying basic position and movements, and then you learn the transitions between the two. Either vertical transitions or horizontal (barrel rolls). And of course carving; head down inface and outface, head up inface and outface.