Q:

Symmetric part after applying FFT is for which frequencies?

I've got a 4096 samples long 44.1 kHz audio-clip. After applying the FFT to it I get 4096 frequency bands.
Each band would then span 10.77 Hz (44100 / 4096).
I've been told the 2nd half of the frequencies is conjugate symmetric to the first half.
Considering this is my calculation above correct or did I miss something important?

A:

That's pretty much correct - for most common complex-to-complex FFTs with purely real inputs (i.e. all imaginary parts zero) the first N/2 output bins (0..2047 in your case) are typically the only bins that you will be interested in. The first bin is DC (0 Hz), and bin N/2 corresponds to Nyquist (Fs/2 = 22.05 kHz), which is not normally of interest. Bins above N/2 are just complex conjugate "mirror images" of the bottom N/2-1 bins.
See this answer for more details.

