avi is a containor file .. the actual file type inside could be anything, but my guess is H/X.264 or Matroska. (Matroska is generally a containor file itself but I believe there is a specific Matroska video format also; not sure) http://en.wikipedia.org/wiki/Matroska
I'm a night owl lol I'm actually from the same land mass as you.

You won't have problems if you use VLC .. but pripla's suggestion is ok too.