The factions of TFA

It appears there will be 4 factions in TFA: The "Republic" , The Resistance, The New Order and the Knights of Ren. We have not heard anything on how the "Republic" plays into this. We know there is/was a Republic as it has been mentioned a few times. Someone posted the wording on the package of the resistance fighter that they are well armed and trained but must use strike missions against the New Order because they are out manned. I was under the impression the New Order was going to be weaker than the "Republic". Are we going to find out the "Republic" has been over thrown by the New Order? Is this going to be set up like the PT where the politics play a huge role? It seems the opening crawl is going to take about 10 mins to read to figure out what is going on in the galaxy far far away after 30 years away.

I know there will be books to fill some of this in but the average movie goer will not have read the books leading up to TFA.