Hi,
In short there are a few types of CG, trading, combat, exploration etc
You sign up at the station in the Galnet message or on the thread in question and do the activity. Bounty/combat vouchers, exploration data etc must be done at that station for it to count but you can sign up and hand in any data you already gathered before the CG started.
For this next bit I have underlined
rank and bolded
tier since they are different and many people get confused:
You will be assigned a
ranking depending on your progress compared with other CMDR's (top 5%, top 15%, top 50% etc). The more you contribute the better rewards are.
The global progress is shown in
tiers and can be seen opening the mission in the left hand panel. The number of
tiers vary from CG to CG, rewards increase for all
ranks.
If the top
tier is reached (the bar is filled) then the goal will end early, regardless of any time left on the mission timer.
Let me know if you have further questions and Good luck
