Active and passive crossovers do the same thing but jsut in a different way. Active are typically used on the rcas while passives are usally the ones that come with your speakers.
Active crossovers use processors to tell the signal where to go so there is no signal loss. Passive crossovers use resistors and coils to tell the frequencies where to go and tend to have more loss than active. Crossovers are basically traffic cops telling the signal who should go where, splitting up the signal. What amps are you using? Some amp have built in crossovers and will have rca outputs so you can hook to the other amp eliminating the need for extra crossovers. There are a few different ways you could set it up depending on the head unit and what the amps you have picked can do.