Sometimes, in a situation like this, WikiPedia is your friend. FOV seems to be Field Of Vision or Field Of View. Something I have not heard of in the books/manuals I have read. AOV did not have an answer though. FX is "FX format, Nikon's nomenclature for the full-frame digital SLR" (copied from WikiPedia) And DX is digital format; their explanation seems quite informative.
Hope this helps.
"The Nikon did the work; I just happened to be behind it at the time." TP