There is only one pin
on the Pi that is capable of producing pulses in this way (GPIO pin
18). This will be connected to the control pin of the servo. The
power to the servo is provided by an external battery as powering the
servo from the Pi itself is likely to cause it to crash as the Servo draws too much current as it starts to move. Servos require 4.8-6V DC power to the motor, but the signal level (pulse output) can be 3.3V, which is how its OK to just connect the signal line directly to the GPIO output of the Pi.
Servo motors generally come with three pin sockets attached. The red and brown sockets supply power (positive to red) and the third yellow or orange socket is for the control signal. To link the socket to the breadboard, use the male-to-male jumper wires.