Use of RC circuit in amplifier output stage
Let's look at the two things that you are asking about. 

1) think about how the amplifier works. Many amplifiers use a bipolar power supply so that they can produce both positive and negative waveforms at the output. 

Your amplifier uses only a single positive power supply rail. So now think about what DC voltage is present at the output pin of the amplifier chip. Then think about why a large capacitor is needed in that spot. 

2) That series RC network from the amplifier output to ground is called a "Zobel Network". Look it in Google.