DD-WRT binaries are split in to a few categories...
- Build number
The builder is the person that made it. Brainslayer and Eko are the two builders. Eko's builds are the NEWD and NEWD2 builds, they're based on a different wireless stack iirc.
The build number is, well, just an incremented number. Use the one that's recommended, the most recent might have problems (these are equivalent to in-dev builds and aren't all necessarily stable or even bootable).
The version is one of "mega", "std", "mini", "micro", and a few others. std is the standard, while the mini and micro images are smaller (for devices with less flash), and the mega build is huge with a million features you won't use. There are also a few special versions, like the "usb" one (which adds support for devices with USB ports, although I think the standard build also has some USB support), and the "voip" one which has some VoIP features.
The platform is usually "generic" but sometimes there are tweaks for specific hardware models, so you'll see a vendor or a model number there.
Now, read the wiki page on this router very carefully. Apparently a filesize limit for succesful flashing has been found, and newer brainslayer builds are too big. You might check if Eko's builds are small enough (they vary somewhat). Now, note that that wiki page specifically says that dd-wrt.v24_std_generic.bin is okay for this router, but keep in mind the filesize limit. Or, for the Eko builds, NEWD_std-nokaid.bin (you can look up in the wiki the practical differences between eko and brainslayer builds).
And that's all you need to know. Look to see if the current recommended brainslayer build is over the size limit. If it is, I'd just use the current NEWD build (assuming it's under the limit). Bottom line, the wiki page has plenty of info on it. Read it carefully. Installing DD-WRT is not really for basic users, so if you're not comfortable interpreting the info available to you you should probably consider sticking to your stock firmware. That said, you can always ask in the DD-WRT forums.