A speaker and amplifier combo is a guitar amplifier and speaker in one box. It covers a wide range of size, weight and output power from the small practice amplifiers to the larger amps. The biggest combos are usually rated at 100 watts and have one or two speakers. Anything bigger would become too big, bulky and difficult to carry so that is when the separate amplifier head and speaker cabs come into their own. Valve combos are always a lot heavier than their solid state equivalents so bear this in mind when choosing one.