Do you mean what is the difference between ISO / UDF ?
this may help for starters if that's your question - there's is probably a much better explanation on this forum, but that was from a quick search. My normal setting is ISO/UDF - in that link it is mentioned this has caused problems - never noticed any myself - thought it was the default Nero setting, or maybe it's a template I modified, I cannot remember as it's long ago now
I change to UDF when I have files larger than 2GB's, which the ISO format does not support. This normally for me is files around 3-4GB (avi or TS files). Strangely, I have seen vob's that are larger than 2GB. I always believed the standard for vob's was 1GB tops - apparently not.