The campaigns are the stand-alone tasks with enemy-bots.  The Journey opens at 8 lvl. You can earn Credits, Celestium, XP and the upgraded module via completing campaigns. 
There are only 7 campaigns - 7 Sectors. The player participates in some battles in each sector with the enemy-bot. After each fight, the player gets Credits, Celestium or XP. The player can see the enemy before battle and prepares for this. Also, after losing you have to repair the ship. And try again. The enemy-bot will be the same as it doesn't change. 
After completing sectors the players get the reward and upgraded module. You can see the reward on the main screen of each journey.