A high current amplifier has a very large transformer with a compliment of large capacitors. A SS amp has an array of semiconductors (transistors or mosfets) that are either cascaded or cascoded. These devices are connected to the transformer and capacitors and function as variable resistors to create a large, powerful signal that is identical to the small input signal coming in from the preamp. That large, powerful signal drives the speakers. The Capacitors and Transformer are energy storage devices. They provide the peak power needed as the music signal varies from low to high. Imagine having a big rheostat that ranges from -60 to +60 volts that is connected to a speaker. If you could turn the dial back and forth fast enough to mimic a musical signal- you could make music. A tube amp functions much the same way. The tubes get the preamp signal and vary their high level output voltage to mimic the musical signal. The output of most, but not all tube amps goes through transformers. That limits their current carrying capability and that is why tube amps generally have the same power rating for 16, 8 and 4 ohms. SS amps can output higher power levels into lower impedance speakers up to the point that the semiconductor devices overheat and go up in smoke. To demonstrate, apply a dead short across your SS amplifier. (Although many modern SS amps have overload protection devices which kind of takes the fun away). Very simplistic terms, but that is how any amplifier works.
