There is three types of this route:
❶ "All Stop" service, which follows from Brooklyn through Downtown Manhattan to Midtown Manhattan and backward with all said stops.
❷ "Midtown Express" service, which follows from Brooklyn to Midtown Manhattan skips stops in Downtown. It serves on weekdays rush hours in the peak direction only.
❸ "Downtown Express" service, which follows from Brooklyn to Downtown Manhattan only and terminate at "State Street/Battery Place" (after "Frankfort Street/Pearl Street" follow to State Street as backward direction, does not Midtown). In Manhattan, this service starts at "Church Avenue/Barclay Street" and then through "Park Row/Spruce Street" buses runs to Brooklyn. It serves on weekdays rush hours in the peak direction only.
Full information you can see here