I just mean that you are not actually buying and selling to another physical person, you are taking a 'bet' against whether the market goes up or down. So if everyone was correct on their positions then IG would lose money because when people get it wrong they make money, when people get it right they lose, right? Taking the position much more like a traditional bookies in that sense.
Correct me if I'm wrong but it's that distinction that means it's a bit daft that you can't trade stocks because the shares are unborrowable, because IG doesn't own the shares to begin with. It tracks the market and you bet on it going up or down?