What is the function of this op amp and how it function?
It's a sallen key 2nd order low pass filter
Basically it's a unity gain non-inverting amplifier with two resistors and two capacitors around it: -


And it has a frequency response typically like this (butterworth Q factor): -

It can be used as a peaking filter: -

If you choose the component values correctly you can get it to produce a resonant peak and I would say that that is what the values used in the OP's diagram are indicating.
So if you plug the resistor and capacitor values into the link at the top of this answer, you'll get a bode plot like so: -

ζ = 0.14832396974191 or, Q = 3.3709993123162. fc = 715.34827161934[Hz]