I have found OpenCV code that uses CvGaussBGStatModelParams structure, cvCreateGaussianBGModel, and other related functions. However, I haven't been able to find any explanations for how they work and how they are to be used and what they mean.
Any help would be appreciated.
These functions are undocumented (at least as far as the manual goes). However, if you look around in the source, you will find them in src/cvaux/cvbgfg_gaussmix.cpp. In there:
This is based on the "An Improved Adaptive Background Mixture Model for Real-time Tracking with Shadow Detection" by P. KaewTraKulPong and R. Bowden http://personal.ee.surrey.ac.uk/Personal/R.Bowden/publications/avbs01/avbs01.pdf The windowing method is used, but not the shadow detection. I make some of my own modifications which make more sense. There are some errors in some of their equations.
That link is probably a good start for you.