This is a slightly different version of your oscillator circuit. This one's an RF oscillator for a radio transmitter -
View attachment 58320
That transistor is your Q2.
Q1 in your circuit acts as a conductive switch, it provides the bias provided by the 47k resistor in my circuit. This bias voltage is necessary for Q2 to oscillate.
That filter I mentioned before is called an "RFC" - Radio Frequency Choke, same as the one coil in this circuit. It allows the collector voltage to bounce up and down like a spring. Dumb analogy, but it works.