What does "Lag" mean in terms of Cross Correlation? I am working on a program using the Essentia library for audio analysis. I've implemented the Cross Correlation algorithm (here: http://essentia.upf.edu/documentation/reference/std_CrossCorrelation.html), but I'm not sure if I really understand the output. Sadly, barely any of the description on that page makes sense to me. I do not have a math background, and only a cursory understanding of frequency analysis / signal processing.

So... can anyone explain what the optional parameters (minLag, maxLag) do here?
using the simplest definition of the cross-correlation:

$$ R_{xy}[k] \triangleq \sum_n x[n]\,y[n+k] $$

the "lag" is the displacement $k$.  (i am being deliberately vague about the limits to the summation.)  in the correlation $x[n]$ is lagging behind $y[n]$ by $k$ sample periods.