I do not know what the RAW image is for.
The .001 and up files are your video splitted into many parts with a fixed size. You must join them into one file when you have downloaded every part. One program which can do this for you is Mastersplitter from
http://www.tomasoft.com/ . It's shareware but who cares.
The par2 file contains information about the files you downloaded (like size and checksum). So can control whether you downloaded them correctly (usenet is not always easy). The program to use is at
http://www.quickpar.org.uk/ . This is optional, you do not need to do this check.
Hope this helped.