Here is the op-amp circuit, which is found in this datasheet on page 5:
I have boxed, in red, the part of the circuit that I am confused about. What is the point of having this? Thanks in advance.
It is a Zobel network also known as Boucherot cell, meant to stablize the amplifier when no load (speaker) is attached. It compensates the increasing speaker impedance at higher frequencies and prevents high frequency oscillation.
(1) What Jippies says.
(2) The Boucherot cell (seen here) is a special case of a Zoebel network.
For speaker application see section "Zobel networks and loudspeaker drivers".
Original 1923 paper is : Zobel, O. J., Theory and Design of Uniform and Composite Electric Wave Filters, Bell Systems Technical Journal, Vol. 2 (1923), pp. 1–46.
Image of full 1923 article here:
Munted text version here: http://archive.org/stream/bellsystemtechni02amerrich/bellsystemtechni02amerrich_djvu.txt