electret mic has built in amp which is powered though R1 also acting as load resistor.
R3 is used to mathc impedance. C1 is used to isolate DC between Mic and Q1 but allow audio frequencies to pass (hence large value).
C3 and C4 are "grounding" capacitor for RF but not for audio frequencies (small value). R2 is biasing resistor for base of Q1.
C4 and L1 are tuned circuit that should be adjusted to some FM band frequency 88-108MHz. C6 is used as feedback to turn Q1 stage into oscillator. without it, this would be only amplifier. R4 is input resistor for Q1 for RF frequencies. (recall that base of Q1 is "grounded" for RF through C2 and C3; Q1 is therefore operating in Common Base mode, emitter is input, collector is output and C6 takes small part of output signal and brings it to input - when this arrives in phase you got oscillator).
rest of the circuit is the same, except that Q2 is in Common Emitter mode.
R5 is biasing resistor, there is LC tuned circuit and antenna is connected to collector.