By setting up a network of resistors we can amplify a signal keeping it's original shape. To do this, a voltage divider is placed at the base to set an "offset", this offset will allow the waveform to go up and down. Then, a resistor is placed at the base so the signal doesn't get's amplified too much the same goes for the resistor at the waveform generator.
You mess around with it to learn how transistor biasing works.
