Wat is Spot, forward and premium-adjusted delta?

The spot delta of an FX option is the amount of the base currency, per unit of notional, to trade in the spot market to hedge it: $\phi e^{-r_f T} N(\phi d_1)$, with $\phi = 1$ for a call and $-1$ for a put. The forward delta is the amount to trade in the forward market, $\phi N(\phi d_1)$. The premium-adjusted delta corrects either for a premium paid in the base currency, which is itself a position in that currency: $\phi e^{-r_f T} (K/F) N(\phi d_2)$ (spot) or $\phi (K/F) N(\phi d_2)$ (forward).