The circuit is an VXO with buffered output. It operates on 20-meter amateur radio band with the output voltage about 0.2 Vp-p.
The crystal frequency is pulled by tuning the variable capacitor CV1 about 36Khz with only one crystal (Y1), and 250Khz by using two crystals Y1 and Y2. The first configuration stability is much better than using two crystals. However, if you need more frequency variation, use two crystals and you have to pay the cost by getting less stability. By the way, the value of the inductor L1 is critical to achieve the most frequency variation. You can use it in transmitters, receivers and transceivers with good results.