From here. Of course support for Red hat is gone. Now Red Hat sells the enterprise edition. Or you can get the open source which is now called Fedora. The md5sum file is a text number. When you click on it you will see a number in your browser window, copy it to notepad and save it, then after you download the iso you use md5summer to check if it got downloaded exactly right and is the same file that it's suppose to be. You can read about it here.
I am right now staring at Linux Redhat iso folder which contains i386 folder and in it there are four iso files named "enigma-i386 disc1.iso, enigma-i386 disc2.iso and two others with different names : enigma-SRPMS-disc1.iso and enigma-SRPMS-disc2.iso. Now what I want to do is install RedHat Linux in a computer I have. Which two iso files should I download? There's also a file in same folder named MD5SUM. What is this file? Do I have to download all files listed inside this folder?