This is a dang good video that defines the terms interlace and progressive video and what the hubbub is about concerning 720p and 1080p HD videos.
It is spot on about helping you understand what your camcorder can record and how it does it.
This video was created in 2007; at the time there were limits as to the length of what you could upload to YouTube and the type of videos you could upload. Although he is talking about high definition videos the actual YouTube video displays at 240p.
I went looking for more about TechnologyEvangelist.com but it seems that everyone have left the building. The site is on hiatus and the principle writers have gone to new projects.