What distro is this? I suspect that the two Binary iso files are CD versions of the distro and the DVD iso is the complete thing on a single DVD, but without know which distro that is only a guess. The MD5SUM and SHA1SUMS are files that contain the MD5SUM or SHA1 values from the iso files. You use these once you've downloaded the iso files you want and compare the values you get to the ones provided in these files. If they match, then your download was good. If they don't, then the download had a problem. Note that you really need only one of the two.
I'm also guessing you're currently on Windows, in which case CDBurnerXP
is a good burning program. As for writing on the disc again, unless you're using RW discs, that isn't likely. The iso files are complete disc images and are likely to take up the entire disc.