Second-Order Low Pass Filter Configuration
This is an example of a Sallen-Key op amp.  Most second order amplifier designs require 2 op amps.  The Sallen-Key's clever design accomplishes this using only 1 op amp.

A mathematical discussion of the low pass Sallen-Key op amp can be found here.

For a simpler "thought" explanation of how the 2 capacitors work listen to this video starting at about 1 minute 15 seconds.  

If you can not view the video, the video essentially states that C2 (in your diagram) appears as a short for all high frequencies to ground.  Because of this, the output of the op amp will be very close to ground at high frequencies.  Consequently, C1 (in your diagram) also shorts all high frequencies to what appears very close to ground at the output of the op amp.

Also, Sallen-Key amplifiers are usually used in unity gain mode which would not use RA nor RB (in your diagram).  Instead, a unity gain amplifier would simply connect the output of the op amp to the negative input.  Adding RA and RB allows for gain adjustment.  But also opens the door to other types of op amps designs as the 1 less component count of the Sallen-Key design is no longer an advantage after adding the 2 extra resistors.

The roll off (what you are calling attenuation) calculations of a first order filter can be found here.  Basically it is 20dB/decade.  A second order filter is double that or 40dB/decade.  (Note, the linked article is using 6dB/octave which is about 20dB/decade.)