This is for the Factions multi-player feature of the game. First you must choose your faction when you first boot up multi-player, then you must survive 12 weeks (84 matches) to finish that faction's story-line.
Every couple games there will will be an event you must do either to add to your clan population, or lower the amount of people you will be losing. This is done by choosing what you will be focusing on in the next 3 games after the event starts, such as downs, executions, downs with a certain weapon, revives, heals etc. There will be some days where the event will be a potential clan wipe which will make you restart from week one, in these cases I recommend you save heals for these situations, because they are the easiest if you put on the first aid 2 skill (correct me if I'm wrong).
If you have questions or corrections, please post here, I'll do my best to answer and help you. :)