The speaker and amplifier combo is an electro acoustic guitar amplifier and speaker in one box. They vary in range, size, weight and output power from the small practice amp to the larger amps. The bigger combos are usually rated at 100 watts and have one or two speakers in and perhaps the added advantage of digital effects.
Bigger amplifiers will become too big and bulky to carry so when you are at this stage you should consider a processor such as the Boss AD3 which will connect directly into the band PA system.