Positive CC is used to purchase expansion attempts in the next cycle.
The expansion attempts will be purchased at the end of the current cycle based on the prepared systems list. You can purchase up to 10 expansion attempts in a cycle provided you have enough CC.
CC enables expansion attempts, without positive CC you will not be able to prepare systems to purchase expansion attempts for the next cycle.
Once you have purchased an expansion attempt, in the next cycle you will be able to attempt to expand into that system. You don't have to pay for this again so even if you have a negative CC balance in the current cycle you will still be able to attempt the expansion.
Provided your expansion efforts beat the opposition then the expansion will succeed (excusing bugs) then it will become a control system in the next cycle. An expansion will also fail if gaining control of the system would have left you a CC deficit in the next cycle.
The more control systems and successful expansions that you have the higher your powers standing in the game. There are significant bonuses for the powers in positions 1 to 3 in the rankings. You need to be at a Rating 2 (100 merits) to benefit from these bonuses.
That's pretty much it, hope I have answered the question.
