The input is being amplified and is push-pulling the speaker coil...
By 'completely' do you mean "The 10uF cap is passing frequencies X to X and attenuating frequencies X to X, thus biasing the transistor, whose gain is 100, etc. etc. etc."?
If that's the case... it may be easier if you ask questions on what you don't understand? If you don't understand any of it, I'm afraid the explanations would require a bit more fundamental knowledge on your part.