Bipolar transistor basics
When Q1 is off Q2 turns on, (with Q2's "base" at 0.7v), and the output line goes low, (near 0v). 

When Q1 is turned on Q2 turns off, and the output returns to the voltage determined by the resistor divider.  

This is assuming the ouput line connects at R2-R3, as your connection dot is shown offset.