It goes to something called convertible RP. You can see the amount you have at the top of the screen right by your SL amount. You earn it through achievements, and through regular matches as a mirror of the normal RP you earn.
It’s used by paying GE, which converts it into actual research points. 1 GE=45 RP.
It’s basically useless, and buying RP is not that good of a deal.
So the grind to unlock all mods for 20 german vehicles was basically useless, thanks Gajin to give me RP’s for free just to buy them. How useless. I was really hoping that the grind was worth it to get my first useful jet faster.
Well, it’s still pay to win, but thanks for clarifying.