It means that when the neutrinos hit electrons, the electrons are moving preferentially in the same directions that the neutrinos were moving. So when we are building a water Cherenkov detector for solar neutrinos, the Cherenkov signal will be coming from the direction of the sun. This is very advantageous to suppress background and because of the daily and annual movement of the sun we can alo suppress other (nondirectional) detector bias effects that could distort a neutrino signal from the sun very effectively.