In an FFT you can use a
windowing with different length, which is called size
in AUDACITY.

The size 2048 means you don't take
all 44100 samples, but only 2048, you do
an FFT with these 2048 samples and move the window
so that the windows overlap and do an FFT again.

This is done up to the end of 44100
sampling points and forms an average of all determined FFT.

For the frequency
resolution this means now: Frequency resolution DDf
= 44100Hz / 2048 = 21,533Hz