OK, this is a parallel tuned circuit. The frequency of interest will be determined by F=1/(2*Pi*[SQRT(L*C)]) where L is in Henry and C in Farad. This means that at the selected frequency there will be a high resistance (impedance in AC terms) from the top of the coil/cap to the bottom of the coil/cap. All the other frequencies will be shorted out to GND (the bottom of coil/cap should be connected to GND)
If you want to amplify the signal, normally a small capacitor is used to feed the signal available at the top of L and C to a amplifier stage that will not load this tuned circuit i.e.. it must have a high input impedance, and for that reason a FET is often used or a tap near the bottom end of the coil where the impedance is lower to drive a bipolar transistor amplifier stage.
This is a very crude and basic explanation and you should be able to find volumes on this and how to design on Google like the one's below
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