In Campaign Mode, the player has to complete several campaigns like the Myriad Campaign. In the begining, you can only play the Consortium Campaign, you can unlock the Myriad Campaign by completing "The Final Step" in the Consortium Campaign.
In Skirmish Mode, you can play alone with the AI. Unlike multiplayer mode, you can select any race and any colour for the other player. You can use this mode to train yourself for Campaign Mode or Multiplayer, especially Multiplayer because the players are extreme profesionels.
In Multi player and Bluetooth Mode, you have to connect to a nearby Wifi source in order to play these modes. You can play with Starfront players around the world but must connect to the internet, for Bluetooth Mode, you have to turn the Apple device's bluetooth and connect with another nearby player in order to play Bluetooth Mode.
If you're playing in Bluetooth Mode, you better play it farther from your opponent or else your base's position will be revealed, leading him/her into an easy victory!