Describing the question in the title further,
There are three classes of spermatogonia: stem cell spermatogonia, proliferative spermatogonia, and differentiating spermatogonia.
In common literature, there are following three subtypes, namely mentioned in the below Wikipedia article:
There are three subtypes of spermatogonia in humans:
Type A (dark) cells, with dark nuclei. These cells are reserve spermatogonial stem cells which do not >usually undergo active mitosis.
Type A (pale) cells, with pale nuclei. These are the spermatogonial stem cells that undergo active mitosis. These cells divide to produce Type B cells.
Type B cells, which undergo growth and become primary spermatocytes.
I am unable to find anything relevant about the "classes" anywhere else (and I do not have full access to the mentioned textbook).
Although I don't have full access to this book, here is the preview to the subsection in the text in ScienceDirect.
(You may find in page to locate the above line)
Additional Note : AL is a newly discovered subtype of spermatogonium. So it's Ad, Ab, B and AL now.