Impress them with this!
Refer to it as the Frequency Dividing Network for full shock value!
Track Rat explained it well.
You have two types or crossovers:
1- Electronic (sometimes called Active)
2- Passive
Electronic crossovers usually offer the benefit of allowing you to adjust the crossover points. They also allow you to set the gain of that frequency band at it's output. This is helpful because then you don't have to worry about the actual power rating of the amp that you are using to feed each speaker set. If the amp is too loud for the horns, you can turn it down at the crossover so that the signal getting to the amp is lower. There are many cool things about this that would take too long to explain (well, I just don't type as fast as I talk or think!), but it is cool none the less.
Also, Electronic crossovers utilize more of the potential power of the amp.
In addition, Electronic crossovers will usually offer a selection of how many db of cut will happen at the crossover point. This is needed because a filter is applied at the crossover point, and since filters usually take at least 1 octave before they attenuate sound by at least 6 db, if you didn't provide some kind of cut in the volume at the crossover point, the frequency response of the cabinet/speakers would not be optimized. You would actually have a boost at the crossover point because there would be a doubling of power due to two speaker playing the same frequency. Different cabinets and speakers and combos of both would require different Attenuation and Slopes (this is the db per octave at the crossover point) to optimize is for it's design. Some require up to a 18db cut at the crossover point.
Passive crossovers utilize a Capacitor and a Coil. Each is in charge of filtering out the frequencies that don't belong to the speaker that is not optimized for that frequency range.
They also so not offer you the ability to adjust the crossover point. This makes them more of less specific to the speaker/cabinet design combo because cabinet design and speaker design combinations can play off each other quite a bit, and a crossover should ideally be applied that matches what is needed for said combo.
The main thing that you need to know about crossovers and how to apply them to a specific speaker/cabinet combo is what the speaker/cabinet combo needs for a crossover point, and how many db of cut at that point. Usually you can find this info out from the manufacture. If not, well, good luck. You better know how to look at the specs of the speaker and the design of the box and make your own conclusions about the proper settings. This is the folly of trying to build you own speaker cabinet without knowing what you are doing, or with no regards to how it will interact with the speaker components that you install. The box could potentially sound like crap without a proper crossover design.
Anyway, this gets really deep, and beyond the scope of what you needed to know!
Good luck in the interview.
Ed