Jon, typically a rectifier changes AC current to DC current, and in this case with the CPP-2 it also steps it down from 120VAC to the required 12VDC or 24VDC as needed.
An inverter, on the other hand does just the opposite; DC voltage is changed to AC voltage. Think of using your car battery at 12VDC coupled up to say a 1000w 120VAC inverter to power things like laptops, dvd players etc in your vehicle.
Of course rectifiers or inverters are used in all kinds of applications for relatively low voltage, low amperage uses up to very high, very large industrial uses.
I have most recently worked on rectifiers (135MVA) IIRC in aluminum smelting. These take the supplied line voltage incoming (230,000VAC) and turn it into useable DC current for the potlines.
I believe the potlines main buss runs at 400,000+ Amperes.
Can you say giant bug zapper???