This used to be the most common design for Garage door opener and before that Radio Control and walkie-talkie receivers.
It is a super-regenerative receiver invented by Edwin Armstrong in the
1920's. It operates on a different principle than the regenerative receiver than many of the posts have been referring to.
In the super-regenerative receiver the feedback is increased until oscillation occurs at the intended receive frequency. Periodically (typically at 100KHz or so) the oscillation is stopped (quenched) and then allowed to build up again. Normally oscillators start-up from circuit noise or transients and take a time to build up: if there is a signal present at the oscillation frequency the oscillations will build up more quickly. The speed of the build-up affects the mean operating current of the circuit and so the presence of an input signal can be detected by filtering the supply current. The effective gain of the circuit can be 60-80dB in a single stage.
The quenching can be performed either by a separate low frequency oscillator or by judicious selection of bias components can be arranged to happen automatically, the circuit is then called self- quenching.
Normally the circuit is only sensitive to amplitude modulation but by slightly offsetting the tuning of the circuit it can demodulate FM using what is called slope demodulation.
These days there are many small modules available for remote control at 315MHz, 418MHz or 433MHz that use super-regenerative receivers. Their sensitivity is usually about -100dBm and only cost a few dollars.
First class explanation of a famous old circuit.
My favourite shorter explanation is: " heap powerful magic ".