Before you begin frothing you should always make sure you are using full cream milk or barista blend plant-based milk for the best froth. Milk actually takes on air better cold so it's good to get the head of foam going before your milk starts to steam. The basic difference however if that cold foamed drinks suit cold coffee better as it doesn't require any milk to be heated while hot foam suits hot drinks and has the bonus option of steamed milk along with it if you prepare the correct quantity.