Different roles of a resistor
Resistors R1 &amp; R2 form a voltage divider.  This might be more clear if you draw the resistors vertically with R1 above R2.  The top end of R1 comes from the DC power rail, the bottom end of R2 goes to ground.  The midpoint junction of both resistors is the output of the voltage divider.

This provides the quiescent bias for the output transistors.  Note that this is a fairly crappy bias circuit - the value of the bias voltage varies as the supply varies.  But that doesn't detract from its purpose, which is to bias both output transistors right at the point where they are both slightly turned ON.

The bias network makes this a "Class AB" amplifier - both transistors are conducting for very low levels but one or other of the transistors turns OFF as the signal amplitude increases.

The net result of this bias is that crossover distortion is greatly reduced.