the "shrike-i386" files are the pc install isos that you need, the "SRPMS" are the source code files. you dont need to dl them; but if you order a linux distro, they will sometimes ship them out as well. i ordered rh9 when it first came out and recieved 9 cds in the mail.
the md5sum files are 128 bit dig. fingerprints of the isos. basically, you run a file called 'md5sum.exe' from windows in the dos prompt against the iso you downloaded and it will tell you if its ok to burn the cd. the command would look like this: md5sum -b redhat9_disk1of3.iso. when its done running it will spit out some numbers and letters; if they match what is in that small md5sum text file your asking about, you have a clean download.