Basically, all amps are going to have a preamp, which does tone shaping, a power amp that provides the juice, and speakers. In a combo, they are all in one. If you use a
Separate cabinet and electronics, you can get a head that has preamp and power amp in one box, or somepeople use separate preamps and powe amps.
Generally speaking (though not always) a head will have more power than a combo,and using
Separate speaker cabs mes
It easier to expand